2. 40/45/50/55B-X Main High Voltage system

[Audio] This slide covers the PDU — the Power Distribution Unit — and its role in the high-voltage system. The PDU is the device that takes high-voltage energy from the lithium battery and distributes it to each major component — the traction system, hydraulic system, BTMS, and air conditioning. Its goal is to deliver stable and safe electrical power to every system in the machine. Inside the PDU, there are several key components working together. The input and output terminals receive power from the battery and send it out to each component — two inputs at the top and six outputs at the bottom going to the traction motor, pump motor, air conditioner, BTMS, and others. On the left side are two CAN signal and communication terminals connecting to the VCU and BMS. Fuses and relays protect the circuit by cutting power if overcurrent occurs. DC contactors physically switch large currents on and off to control power flow. Various sensors monitor voltage, temperature, and leakage in real time. And the CAN communication interface continuously reports the current power status back to the VCU and BMS. For service work, the key points are these. If a specific high-voltage component stops working, suspect the fuse or contactor inside the PDU first before looking elsewhere. And before inspecting the PDU under any circumstances, always disconnect the MSD and wait for the system to discharge. This is non-negotiable..

[Audio] This slide shows the internal structure and detailed functions of the PDU. The PDU has two primary functions. First, it protects the high-voltage lines using contactors and fuses that physically connect or disconnect the circuit to protect the system. Second, it converts high voltage down to 12 volts through an integrated DC-DC converter with a maximum output of 2.5 kilowatts. Looking at the main internal components: the contactors are represented as switch symbols at the bottom of the circuit diagram. Each MCU contactor is rated at 250 amps. The fuses appear as zigzag symbols in the middle of the diagram, rated at 20 amps. They blow first in an overcurrent situation to protect the more expensive downstream components like the air conditioner and PTC heater. The interlock loop is a safety circuit — if any connector is not fully seated, it immediately cuts high-voltage power. For connections: the battery connector is where power enters from the battery. The MCU 1 and 2 connectors send power to the traction and hydraulic motor controllers. The air conditioning and PTC connectors supply the compressor and heater. And the DC-DC connectors handle the input and output for low-voltage conversion. For service: if a high-voltage related fault appears, open the PDU and check whether the relevant contactor is operating correctly and whether any fuse has blown before replacing any other component..

[Audio] This slide covers the high-voltage PTC heater and air conditioning system. Starting with the heater: this model uses an air-heating type high-voltage PTC heater. The key advantage over IC forklifts is response speed — there is no engine warm-up required, so the cabin heats up almost immediately after switching on. In a performance comparison at minus 15 degrees Celsius over 60 minutes of operation, this system achieved a cabin temperature of 25.3 degrees Celsius, slightly higher than the previous model at 25.1 degrees. For the air conditioning system: the electric model maintains maximum cooling performance regardless of engine RPM or coolant temperature, because those variables simply do not apply. In a conventional IC forklift, air conditioning performance drops when engine RPM is low. Here, the compressor runs directly off the battery, so cooling output is always consistent. In a performance test at 38 degrees Celsius over 60 minutes, the system maintained a cabin temperature of 24.4 degrees Celsius — equal to or slightly better than the previous IC model at 24.7 degrees. For service: both the heater and air conditioning compressor receive high voltage directly from the PDU. Always treat their terminals as high-voltage components and follow full safety procedures. Also note that both systems operate independently from vehicle motion — the compressor and heater can be controlled on their own, which is important to understand when diagnosing faults..

[Audio] This slide covers the high-voltage cable system and the HVIL — High Voltage Interlock Loop — for the 4.5-ton model series. All high-voltage cables in this machine use orange outer insulation. This is a global safety standard that allows technicians to immediately distinguish high-voltage wiring from conventional low-voltage wiring at a glance, preventing electrical accidents. There are four key characteristics of these cables. Safety — the cables are heavily insulated to withstand high-voltage current and minimize electrical hazard. Efficiency — the optimized design reduces power loss and maximizes battery performance. Durability — the cables are built to maintain long-term stability in construction machine environments with high temperature, vibration, and impact. And HVIL — the High Voltage Interlock Loop — which is the most important safety feature in the high-voltage system. If a fault occurs anywhere in the circuit, it instantly cuts power. The HVIL is a low-voltage monitoring circuit that links all high-voltage components and connectors in a single continuous loop. If any high-voltage connector is physically disconnected or becomes loose, the HVIL circuit detects the break and immediately opens the main contactor to cut high-voltage power. This protects technicians during service work and provides automatic protection in the event of wiring damage. Looking at the layout for the 4.5-ton model: power flows from the battery through the PDU, then out to the traction inverter and pump inverter in a short, direct path. Compared to the 8-ton model, this series has fewer inverters, so the high-voltage wiring path is simpler and the HVIL check points are more concentrated. For service: regularly inspect orange cables for worn insulation or any areas where the cable is being pinched by the machine frame. When a high-voltage error appears, the first thing to check is whether all connectors in the HVIL loop are fully seated. Always remove the MSD and wait at least five to ten minutes for capacitor discharge before touching any high-voltage line..

[Audio] This slide reinforces the key properties of high-voltage cables and explains how the HVIL interlock circuit works in detail. All high-voltage cables are orange — this is the first rule every technician must know. Never touch an orange cable without first measuring voltage, even after the machine has been powered down. Inspect orange cable insulation regularly for peeling, heat discoloration, or any damage. And remember that if any high-voltage connector is not fully seated, the HVIL system may prevent the machine from operating at all. Now let's look at how the HVIL circuit works. Looking at the diagram, you can see a yellow highlighted line running continuously from the battery, through the PDU, to the traction motor, and then to the pump motor. This is a series loop — if any single point in this line is broken, the entire loop is disrupted. In normal operation, when all connectors are fully seated, current flows through the entire loop and the system reads the status as safe, allowing high voltage to remain active. When a fault occurs — for example, a connector is accidentally unplugged or vibration causes a loose connection — the loop breaks. The moment the loop breaks, the contactor inside the PDU is forced open, cutting high-voltage power immediately. For service diagnosis: if a high-voltage error appears and the machine won't operate, the first thing to check is whether all connectors on the HVIL path are fully and firmly seated. The key connection points in this loop are the battery connector, the PDU output connectors, and the motor input connectors. Check each one by firmly pressing them in..

[Audio] This slide covers the detailed specifications of the HDX high-voltage cable. For certifications and standards: the cables are certified to UL758 and UL583 international safety standards, and comply with the LV216-2 cable diameter standard. For electrical performance: the cables are rated for a maximum voltage of 1000 volts DC. Current capacity depends on cable thickness — for example, the largest size, 3 slash 0 AWG, is rated at 280 amps at 85 degrees Celsius. For temperature and durability: the operating temperature range is minus 40 degrees Celsius to plus 140 degrees Celsius, covering extreme cold and heat environments. The cables use a braid-type electromagnetic shield with a coverage ratio of 85 percent or greater, minimizing electromagnetic interference with other systems. For appearance and material: the outer color follows RAL 2003 orange for high-voltage identification. The insulation material is XLPE — cross-linked polyethylene — which provides excellent insulation performance and heat resistance. The jacket material is rated UL94-V0 for flame resistance, reducing fire risk. One important installation note: never force a cable into a tight bend. Each cable size has a minimum bend radius requirement of 4 to 6 times the outer diameter. Bending beyond this limit damages the internal conductors. Always route cables with gradual curves according to the specified minimum radius for that cable size..

★ HDX High voltage connector specification Voltage and Current range 650V unit : 1000VDC Over, 35mm2 = 180A, 50mm2=230A, 70mm2=280A, 90mm2=300A @85˚C Over 350V unit : 500VDC Over, 35mm2 = 180A, 50mm2=230A, 70mm2=280A, 90mm2=300A @85˚C Over 2) Temperature range -40˚C to +140˚C 3) Color RAL 2003(Orange) 4) HVIL (High Voltage Interlock Loop : Protective circuit for High voltage system safety. Normally used for EV) : HVIL Contact System 5) Flame-Retardant Material : UL94-V0 or Higher 6) Shield : Metal Shielding (RFI/EMI Protection) 7) IP rate : IP67 or higher, IPXXB(Unmated), (IPXXD) 8) Standard : LV215.

[Audio] This slide covers the 12-volt low-voltage power supply system — the foundation that must be active before any high-voltage system can start. The 12-volt battery on the left is the starting point for everything. Power from this battery passes through the master switch and distributes throughout the machine. The green dashed area in the diagram represents the optional master switch position. Power is protected and distributed through three main fuses — labeled Power Fuse 1, 2, and 3 — each rated at 60 amps. These fuses feed power through the bus bar to the PDU, BTMS, and various controllers. Three important control and safety devices are shown here. The key switch — when the operator turns the key, it sends a wake-up signal to the system. The fuse box on the upper right of the machine contains smaller fuses protecting individual circuits like the key start and VCU power supply. The emergency switch at the lower part of the machine is a safety cutoff that immediately kills power in an emergency situation. At the lower right of the diagram is the VCU — the Vehicle Control Unit. It receives the key switch signal, gets its power supply, and from there makes all final decisions about machine operation — driving, hydraulics, and everything else. The key message for your technicians is this: before high voltage can flow, the 12-volt system must be alive first. If a technician turns the key and nothing comes on — no lights, no display — do not suspect high voltage yet. Check the 12-volt main fuses and the key switch circuit shown in this diagram first. That is always the correct starting point..

[Audio] This slide shows the HV wake-up signal circuit — how the machine initializes each high-voltage component in sequence when the key is turned. The VCU at the lower left of the diagram is in command. When the operator turns the key, the VCU sends an initialization signal. This signal passes through the relay box, activating the relays, and then distributes wake-up signals to each component. The components that receive this wake-up signal are: the traction and pump inverters, which prepare to drive the motors; the PDU, which prepares to manage high-voltage flow; the HV battery, which prepares to communicate with the system; and the BTMS, which starts up for thermal management. The important design feature here is that this is not a single line — each component receives an independent wake-up signal through the relay and fuse box. And all of these signals operate at 12 volts. Only after all components have received their signals and responded correctly will the main high-voltage contactor close. The practical takeaway for your technicians is this: when the key is turned, high voltage does not come on all at once. The VCU sends signals to the inverters, PDU, battery, and BTMS one by one, and each must respond before the system goes live. If a communication error appears on a specific component, or high voltage fails to come on, check whether the wake-up signal line for that component is intact. A break in one of those lines is often the root cause..

[Audio] This slide shows the complete integrated HVIL circuit — the full safety interlock loop covering every high-voltage component in the machine. The loop begins at the HV battery at the upper left of the diagram. It then passes through the HV safety plug, through the PDU, through the traction and pump inverters, through the air conditioning compressor, and through the PTC heater. After passing through every high-voltage component, the signal must return to the VCU at the lower left. Only when this full loop is confirmed complete does the system determine that all connectors are properly seated and allow high voltage to flow. There is a new component shown here — the HV safety plug near the battery. This plug is part of the interlock line. If this plug is removed, high voltage will not flow regardless of the status of any other connector in the system. The scope of monitoring has also expanded. Previously we covered the motors, but now the air conditioner and PTC heater connectors are also part of the interlock loop. If even one of these connectors is slightly unseated, the entire system will shut down. The VCU monitors this loop continuously. If the loop is broken at any point, the VCU immediately opens the contactors inside the PDU, cutting all high-voltage power. The practical message for your technicians: when a high-voltage error appears, go through every connector on the interlock path one by one and press each one firmly to confirm it is fully seated. The interlock path runs from the battery, through the safety plug, PDU, traction inverter, pump inverter, air conditioning compressor, and PTC heater, and back to the VCU. One loose connector anywhere in this chain will shut down the entire machine..

[Audio] This slide shows the charging system circuit in detail, covering both the high-voltage power path and the temperature and communication monitoring lines. Starting with the HV line — the main charging path. High-voltage DC positive and negative terminals at the upper left connect directly to the HV battery at the upper right. This is the thickest line in the diagram and carries the actual charging current. For service: if excessive heat is generated during charging or charging efficiency drops, always check the connection torque and terminal corrosion condition on this high-voltage cable first. The NT lines are the temperature sensor signals from the charging inlet. NT1 plus, NT1 minus, NT2 plus, and NT2 minus carry temperature data from sensors inside the charging inlet to the BMS temperature monitoring terminals. During fast charging, these sensors watch for connector overheating. If the temperature rises above a set threshold, the BMS reduces or stops charging current to prevent fire. The CC1 and CC2 lines handle connection recognition. CC1 goes from the inlet through a 1 kilohm resistor to ground, confirming the physical connection of the charging plug. CC2 goes from the inlet to the HV battery for final confirmation that the charger is connected. The A plus and A minus lines are auxiliary power from the charger that passes through a diode to wake up the VCU and BMS. The S plus and S minus lines carry CAN charging communication data. For service diagnosis: if a temperature overheat warning appears during charging, check the NT line resistance at the inlet terminals for poor contact before assuming a battery problem. If a high-voltage insulation fault appears only during charging, check the HV DC cable insulation and look for moisture inside the charging port. If the charger is recognized but power is not being delivered, check the CC2 and CAN communication first, and if those are normal, suspect poor contact on the main HV line or a fault with the battery's internal charging relay..

[Audio] This slide shows the full CAN communication network — the nervous system that connects every unit in the machine. It is organized into two independent lines: CAN 1 for powertrain and main control, and CAN 2 for convenience and auxiliary control. CAN 1 is the upper line in the diagram. It begins at the cluster instrument panel's internal termination resistor on the left and ends at the HV battery's internal termination resistor on the right. When diagnosing a communication fault, these are the two endpoints where you should measure resistance. The key units on CAN 1 include the RMCU, PDU, traction and pump inverters, VCU, OBD service port, and BTMS — all the components directly involved in driving and hydraulic operation. CAN 2 is the lower line. It begins at the cluster on the left and ends at the resistor or G-sensor mast on the right. Units on CAN 2 include the monitor, device authentication unit, RMCU, air conditioning unit, amplifier PDS, and G-sensor. Note that the air conditioning unit uses a pass-through connection on CAN 2, meaning the line physically passes through its connectors. For wire identification: CAN 1 uses wire numbers 114 for high and 115 for low. CAN 2 uses 116 for high and 117 for low. Both lines run at 500 kilobits per second. For service: if a full communication error appears across the entire system, measure resistance at both endpoints of the affected line with the key off. You should read approximately 60 ohms between CAN high and CAN low. If you read 120 ohms, one termination resistor or a section of the line is broken. If only one unit — for example, the air conditioner — stops communicating, remember that pass-through connected units can break communication for everything downstream when their connector is removed. Check that connector first. And note that there are separate OBD service ports for CAN 1 and CAN 2 — make sure you are connected to the correct port for the system you are diagnosing..

[Audio] This slide covers the parking brake system circuit and how each stage of the process works from the operator's input through to the physical brake release. The system begins at the parking switch next to the operator's seat. When the operator presses the switch, signals travel through three wires — numbered 322, 323, and 324 — to the VCU. Three wires are used deliberately so that if any one wire breaks or shows an abnormal voltage, the VCU detects a switch fault and keeps the brake engaged for safety. When the VCU receives the signal, it sends a command to the auto parking relay in the relay box below. The important detail here is that the VCU does not send positive power — it connects the ground line through the signal wire. Constant positive power is already present at the relay coil, so the VCU simply completes the circuit by providing the ground path, and the relay clicks on. When the relay activates, power flows through the white wire to two places. First, it goes directly to the electromagnetic brake and physically releases it. Second, it loops back through the green wire to pin 75 on the VCU. This return signal is how the VCU confirms that the relay actually sent power as commanded. There is also a diode in the circuit that absorbs reverse voltage when the brake switches off, protecting the VCU from damage. Finally, the VCU receives a physical feedback signal from the C pin on the brake unit confirming that the brake has mechanically opened. Only when all of these signals align does the parking indicator disappear from the cluster and allow the machine to move. For service diagnosis: if a parking error appears, check three things in order. First, is the VCU sending the ground signal on the correct wire? Second, is the relay sending power back through the green wire to pin 75 on the VCU? Third, if power is flowing correctly but the error persists, suspect the physical feedback signal from the C pin on the brake unit. And if a fuse blows every time parking is released, the diode protecting the circuit is likely burned out — check that component before assuming a wiring short..

3. 40/45/50/55B-X Hydraulic & PowerTrain.

[Audio] This slide shows the overall layout of the hydraulic system — how electrical energy is converted into hydraulic power and distributed to each work function. The hydraulic system follows the oil through the machine. The hydraulic tank stores all hydraulic fluid and is located at the rear of the forklift, supplying clean oil to the entire system. The suction hose draws oil from the tank into the pump. If this hose is kinked or blocked by debris, severe cavitation noise will come from the pump — always check this hose during inspections. The return hose carries oil back from each cylinder to the tank after work is done. The pump motor and its controller are the heart of this system. They receive battery power and spin the main pump, which pressurizes the oil. On an electric forklift, the pump motor only runs when the operator moves a lever, which is why electric machines are significantly more energy efficient than IC forklifts. The MCV, or Main Control Valve, acts as the intersection point. When the operator pulls a lever, the MCV directs oil to the appropriate actuator — lift, tilt, side shift, or other attachment functions. The priority valve is located upstream of the MCV. When the operator steers while working, this valve sends oil to the steering system first before the work functions, ensuring safe directional control at all times. For service diagnosis: follow the oil path. If lift force is good but steering is heavy, the problem is likely not the pump — suspect the priority valve, which divides flow between steering and work functions. If all hydraulic functions are slow and accompanied by noise, the suction hose may be kinked or the in-tank filter may be clogged, preventing the pump from drawing oil properly. On electric machines, always use the diagnostic tool to confirm the pump controller is sending the correct commands to the pump motor alongside any mechanical inspection..

[Audio] This slide shows the hydraulic circuit diagram with pressure values — how pressure is generated, regulated, and distributed to each cylinder. Starting at the pump: the main pump at position 1 is driven by the electric motor and pushes pressurized oil into the system. Immediately above it is the priority valve at position 2, which sends oil to the steering system first whenever the operator is steering, even during other operations. At the center of the circuit is the MCV at position 3, which contains the pressure relief valves that protect the entire system. The first relief valve is set at 215 bar and protects the lift and tilt circuits — this is the maximum system pressure. When lift or tilt reaches the end of travel, oil bypasses back to the tank at this pressure to protect the pump and hoses. The second relief valve is set at 140 bar, with a possible range up to 170 to 180 bar, and handles auxiliary attachment functions. The return filter bypass opens at 2.5 bar — if the return filter is completely blocked, oil bypasses the filter directly to the tank rather than letting the hose burst. If this bypass is active, filter replacement is urgent. For the working actuators: the steering unit and cylinder at positions 4 and 5 operate at a relief pressure of 135 bar — lower than the main system pressure to protect the steering circuit. The lift cylinder at position 6, tilt cylinder at position 7, and auxiliary cylinder at position 8 handle the main work functions, each with their own valve logic. For service: hydraulic diagnosis starts with pressure measurement. If overall force is low, connect a gauge at the MCV port and pull the lift lever to full travel — you should read 215 bar. If that pressure is low, the pump or the main relief valve is the suspect. If lift is fine but steering is heavy, check the 135 bar at the steering unit — the priority valve may be stuck and not directing enough flow to steering. If the return filter bypass is active, replace the hydraulic oil and filter immediately — contaminated oil circulating through control valves dramatically shortens their service life. And remember: the first relief valve handles lift and tilt, while the second relief valve handles auxiliary functions. Use this to narrow down which circuit has a problem..

[Audio] This slide matches the hydraulic circuit diagram from the previous slide to actual photos and a 3D model of the real machine, so technicians can identify each component by sight. Position 1 is the main pump. In the photo, you can see it mounted next to the motor with the orange high-voltage cable connected. All hydraulic energy originates here. Position 2 is the priority valve, located in the cluster of hoses inside the machine. When the operator steers, this valve temporarily reduces flow toward the MCV at position 3 and redirects oil to the steering unit at position 4. Position 3 is the MCV — the large valve block located beneath the operator's seat. This is where the first relief valve sets lift and tilt pressure at 215 bar, and where the second relief valve sets auxiliary pressure at 140 bar. Position 4 is the steering unit, located directly below the steering column. It meters oil proportional to handle rotation and limits internal steering pressure to 135 bar. For the working actuators: position 5 is the steering cylinder at the axle, which adjusts the rear wheel angle. Position 6 is the large lift cylinder behind the mast, controlled by the first relief valve. Position 7 is the tilt cylinder for forward and backward mast angle, also under the first relief valve. Position 8 is the auxiliary cylinder for side shift and other attachments, controlled by the second relief valve. For service: when diagnosing lift or tilt force problems, go to the MCV block in the photos and measure pressure at the first relief valve — target is 215 bar. For heavy steering or steering errors, trace the flow from the priority valve to the steering unit and check the 135 bar relief pressure there. For slow auxiliary functions only, check the second relief valve in the MCV block at 140 bar without adjusting the main system pressure. Use these photos to locate each component quickly in the field — reference the orange high-voltage cable and black hydraulic hoses as visual landmarks when searching for ports in tight spaces..

[Audio] This slide shows the three hydraulic pressure checking ports on this machine — the specific locations where technicians connect a pressure gauge for diagnosis. There are three ports in total. The first is the MCV port — one port located at the inlet side of the main control valve. This port is used to check the pressure settings of both the first and second relief valves. When testing, pull the lift or tilt lever to full travel and confirm you read 215 bar. When testing the auxiliary function, confirm 140 bar. If pressure at this port is low, either the pump has failed or the main relief valve has a fault. The second and third ports are both on the priority valve — a P-line port and an LS-line port. The P-line port measures the raw output pressure directly from the main pump, before it reaches any control valves. Use this port to assess pump health directly. If the MCV pressure is low but the P-line pressure is normal, the problem is in the circuit between the pump and the MCV. The LS-line port measures the load sensing signal pressure from the steering unit. This pressure should change when the operator steers. If you steer and the LS pressure does not rise, the steering unit is faulty internally. For service diagnosis: if overall force is low across all functions, start at the MCV port — pull the lift lever to full travel and check for 215 bar. If that is low, then measure the P-line at the priority valve to determine whether the pump is producing correct pressure. If the pump is fine and the MCV reading is low, look for internal leakage or a stuck main relief valve. If steering is heavy, check the LS-line port at the priority valve — if the steering unit is not sending a load sensing signal, the priority valve will not open the oil path toward steering. If only the auxiliary function lacks force, use the MCV port while operating the side shift lever and check for 140 bar..

[Audio] This slide shows the actual physical locations of the two priority valve pressure checking ports on the real machine, matching the circuit diagram to what technicians will see in the field. The first photo at the top shows the steering unit LS-line port. It is located on the side of the valve block adjacent to the steering hoses. This is where you measure the load sensing signal pressure from the steering unit. When diagnosing heavy steering, steer the wheel to full lock and check whether pressure rises correctly to the specified value of 135 bar. If you steer and see no pressure change, the shuttle valve or signal line inside the steering unit is blocked. The second photo at the bottom shows the main pump P-line port. It is located at the branch point on the large main pressure line coming up from the pump, near the relay box. This area can be tight with surrounding components, so confirm the exact location using the reference photos before reaching in. This port measures the raw output of the main pump before any control valve. When overall machine force is low, measure here first to determine whether the pump itself is producing sufficient pressure before inspecting any valves. For field use: the orange high-voltage cable and black hydraulic hoses visible in the photos can serve as landmarks to locate these ports in tight spaces. When doing steering diagnosis, find the LS port first — it is on the steering hose side of the valve block. When diagnosing overall pump output, find the P-line port near the relay box. Measuring at the correct port first saves significant diagnostic time in the field..

[Audio] This slide shows the MCV working pressure port — the location on the main control valve where technicians connect a pressure gauge to measure actual working pressure for each function. The port is located at the front face of the MCV block, directly below the lever assembly. It is protected by a metal cap and chain to prevent contamination, and accepts a standard hydraulic test gauge coupler directly. When accessing this port, be careful not to damage the surrounding solenoid valve connectors with your hand or tools. The target pressure values at this port are as follows. When operating the lift or tilt lever to full travel, you should read 215 bar — this is the first relief valve setting. When operating the auxiliary function such as side shift to full travel, you should read 140 bar — this is the second relief valve setting. Use this port as the first measurement point whenever a customer reports a lack of force in any hydraulic function. The reading here will immediately tell you whether the issue is with the pump and relief valve, or somewhere in the downstream circuit..

[Audio] This slide explains how the hydraulic pump motor is controlled using Hall sensor-based proportional control — a key difference between this electric forklift and conventional IC forklifts. The control works in three stages. First, the operator moves a lever. Second, a non-contact Hall sensor mounted at the base of the lever detects exactly how far the lever has moved in real time. Third, based on that detected signal, the controller adjusts the pump motor's rotation speed to generate exactly the flow the operator is requesting. The key difference compared to older microswitch-based systems is significant. With a microswitch, even a small lever movement triggers the pump to run at full speed immediately — there is no proportional control, which makes precise lifting difficult and wastes energy. With a Hall sensor, moving the lever 10 percent makes the motor run slowly, and moving it 100 percent makes the motor run at full speed. The output is proportional to lever input, as shown by the red line in the graph on the slide. This gives the operator smooth, precise control and significantly extends battery life. For service diagnosis: if an operator reports that lift response is no longer smooth — for example, the load jumps or the movement is abrupt — suspect the Hall sensor at the lever base. A failing sensor may be reading lever position as all or nothing instead of a smooth gradient. Because it is a non-contact sensor using magnetic principles, it does not wear out at contact points like a microswitch does. However, metal particles or debris interfering with the magnetic field can cause erratic readings. If the pump motor keeps running after the lever is released, or spins at high speed from a very small lever movement, use the diagnostic tool to monitor the Hall sensor voltage output in real time. With the lever at neutral, voltage should be approximately 2.5 volts. Moving the lever fully in either direction should produce a smooth, linear change between 0.5 and 4.5 volts. If the voltage is stuck at 0 or 5, or if it jumps instead of changing smoothly, the sensor is faulty..

[Audio] This slide shows the physical port configuration of the Buchholz 125 liter per minute MCV and the critical assembly instruction for the spool valve. The key specifications: the MCV is made by Buchholz, uses an open center design where oil circulates back to the tank when no lever is operated, and uses Hall sensor control for precise proportional operation. It is based on the 4.5-ton LPG forklift MCV and uses the same Hall sensor control type as the 30B-X model. The most critical assembly instruction shown on this slide is: when inserting the spool, make sure the punching mark on the spool faces the port direction. This is not optional. The spool has precision flow control grooves machined into it, and if the spool is inserted backward, flow control becomes impossible or abnormal operation will result. This is a common mistake even for experienced technicians — always verify the punching mark orientation before pushing the spool in. For port identification: the P port receives high-pressure oil from the main pump. The T port returns oil to the hydraulic tank. The A port connects to the lift cylinder. A1 and B1 connect to the tilt cylinder. A2 through A4 and B2 through B4 are the auxiliary ports for side shift and other attachments. The sensor boxes mounted at the bottom are the Hall sensor assemblies that detect lever movement. For service: if a function that was working correctly starts behaving abnormally after MCV maintenance, the spool orientation is the first thing to check — it is wrong often enough to always verify. When connecting hoses, confirm port labels carefully — the P, T, and A ports handling lift flow are physically larger than the auxiliary ports. And regularly inspect the sensor box connectors for oil contamination from hydraulic leaks — oil seeping into the connector pins causes Hall sensor signal noise and unstable motor RPM..

[Audio] This slide shows how the sensor box configuration at the bottom of the MCV varies depending on the number of spools installed — 3, 4, or 5 spool configurations. For the 5-spool MCV, which is the full-option configuration, two sensor boxes are installed. The important note here is that the last sensor in the sensor box is not utilized. There is one sensor position in the box that has no wiring connected and is not in use. If the fifth lever function does not operate, do not assume it is a sensor box fault — the correct diagnosis is a mechanical issue or something else entirely, not the sensor. Do not spend time troubleshooting a sensor that was never connected. For 3-spool and 4-spool configurations, only one sensor box is installed. The 3-spool box covers three lever positions and the 4-spool box covers four. Although they may look the same externally, the internal sensor layout and connector pin arrangement may differ between 3-spool and 4-spool versions. Always verify the part number before replacing a sensor box — do not substitute one for the other based on appearance alone. For Hall sensor measurement values: at neutral position, voltage should read approximately 2.5 volts. When the lever is moved fully in either direction, voltage should change smoothly and linearly between 0.5 and 4.5 volts. If voltage is fixed at 0 or 5 volts, or if it jumps suddenly rather than changing gradually — for example jumping from 2.5 volts to 4.0 volts instantly — the sensor is faulty. And regardless of configuration, regularly check the sensor box connectors for hydraulic oil contamination. Oil seeping into the connector pins is a common cause of signal noise and unstable pump RPM across all spool configurations..

[Audio] This final slide shows the locations of the main adjustment valves on the MCV — the relief valves, the manual lowering valve, and the pressure compensator. The first relief valve, labeled PRV1, is set at 215 bar and controls lift and tilt pressure. It is located at the upper left of the MCV. The second relief valve, labeled PRV2, is set at 140 bar and controls auxiliary attachment pressure. It is located at the upper right of the MCV. When adjusting pressure, connect a gauge to the measurement port first, operate the relevant function, and only then make adjustments. Turning the screw clockwise increases pressure, and counterclockwise decreases it. The manual lowering valve is the emergency device used when the mast is stuck in a raised position due to a system failure. To lower the forks, loosen this screw and the forks will descend slowly. The critical safety rule is: maximum 1.5 turns. Never open this valve more than 1.5 turns. Exceeding this limit can cause the forks to drop suddenly out of control, or the valve itself can be expelled from the body — both are dangerous. Make sure your team knows this limit and emphasizes it clearly during any emergency lowering procedure. The pressure compensator ensures consistent oil supply across multiple simultaneous functions — for example, operating lift and tilt at the same time. This is an internal valve that technicians generally do not need to adjust in the field. For service: never adjust the relief valves without first measuring pressure at the correct port. If lift force is low, measure at the MCV port first. Only adjust PRV1 if the reading is confirmed below 215 bar. The same logic applies to PRV2 for auxiliary functions. After any adjustment, always tighten the lock nut firmly — vibration will gradually loosen an unsecured screw and cause the pressure to drift, requiring another service call. And always remind your team about the manual lowering limit of 1.5 turns — this is the most safety-critical adjustment point on the entire MCV..