In normal circumstances, when you insert the key into the forklift, the controller will perform a self-check for 2 seconds, and you will hear a distinct “click” sound, which is the sound of the main contactor engaging. If you don’t hear this sound, it is likely that there is a problem with the coil of the main contactor. If you hear this sound but the forklift stalls when the speed increases slightly during operation, then there may be an issue with the contacts of the main contactor.
The main contactor is usually located below the control panel or instrument panel. Typically, forklifts have dual-contact contactors with 4 contact points, corresponding to the front and rear ends of the hydraulic and drive modules.
Troubleshooting for Main Contactor Coil Fault:
- Check if the power plug connecting the main contactor to the forklift is loose.
- Verify if power is being supplied to the coil. For this, you will need two steel needles, each connected to one of the two wires of the coil. It is important to keep the steel needles separated to avoid short-circuiting. Use a multimeter to measure the voltage. There will be two voltage readings: when you turn the key, the voltage will momentarily reach 48V and then drop to a holding voltage of 24V. This indicates that the power supply is normal. Also, measure the coil resistance, which should typically be around 76Ω.
Solution: If there is an issue with the coil, it needs to be replaced.
Troubleshooting for Main Contactor Contact Fault:
First, connect one end of the multimeter to the negative terminal of the battery, and then connect the other probe to the front end of the contactor’s contact point. Measure and record the voltage for both modules. Then measure the voltage at the rear end after the forklift is powered on. Normally, there should be almost no voltage difference between the two ends. If there is a significant voltage difference, it indicates contact point erosion.
Solution：Remove the main contactor from the forklift and disassemble it. Inside, you will find the coil and contact point sections. In the contact point section, you will clearly see the condition of the contacts, whether they are eroded or not. Fix the contact point section and use a file to smooth the surfaces of the 4 contacts, ensuring they are at the same height for both front and rear ends.