How to determine if a complete Power Window Regulator malfunction is caused by a fuse, relay, or wiring issue?

Initial Inspection – Confirm Power Supply
1. Check the Main Fuse
First, locate the fuse in the vehicle's power supply box dedicated to the power windows (common numbers include 28, 22, and 12).

Use a multimeter or visually inspect the fuse core for blown wires. Replace with a fuse of the same specification if necessary.

2. Check Relay Status
Locate the power window control relay and use a multimeter to measure the continuity of its coil terminals, ensuring the relay closes when energized.

3. Observe Instrument Panel Indicators
Check the instrument panel for any power window malfunction lights or warning messages. Record the fault codes for later investigation.

Step-by-Step Troubleshooting – Three-Layer Structure: Fuse, Relay, and Wiring

1. Fuse Layer
If the fuse is intact, continue checking for partial blowouts or poor contact; check the fuse holders inside the fuse box for corrosion or looseness.

2. Relay Layer
Follow the "Relay Test" procedure: Connect the red probe of a multimeter to the relay control terminal, and the black probe to ground. Activate the power window switch and observe if a low-resistance path appears.

If the relay coil resistance is abnormal (too high or short-circuited), replace the corresponding relay.

3. Wiring Layer
Use the voltage setting on a multimeter to measure the voltage of the power window motor power supply harness; the vehicle voltage (12V or 24V) should be present when the window switch is pressed.

Check the harness connectors for looseness, corrosion, or breakage; if necessary, remove the connectors, clean them, and re-insert them securely.

Function Verification – Confirm Motor and Speed ​​Control Module Operation

1. Motor Power Supply Check
After confirming the circuit is powered, measure the voltage at the motor terminals to ensure it is within the rated range; if the voltage is normal but the motor does not rotate, there may be an internal motor fault.

2. Internal Motor Check
Measure the motor resistance to confirm the coil resistance meets the technical specifications; abnormal resistance indicates a burnt-out coil or short circuit.

3. Speed ​​Control Module
If the vehicle is equipped with a motor speed control module (PWM control), use an oscilloscope or dedicated diagnostic tool to check if the speed control signal is output normally.

Comprehensive Judgment and Follow-up Handling

1. Fault Location
If the fuse, relay, and wiring are all checked and found to be in good condition, and the motor power supply is normal, the fault can be determined to be internal to the motor itself or the control module, requiring replacement of the corresponding component.

2. Replacement and Reset
After replacing the faulty component, reinstall it and check if the fuse has blown again due to a short circuit in the new component; if necessary, reset the relay's self-test status.

3. Functional Testing
After replacement, perform a full vehicle power window lift test to confirm that the Power Window Regulator in all doors functions normally.

Technical Support and Supply Chain Assurance

1. Ningbo Nanxing Auto Parts Co., Ltd., as a professional Power Window Regulator OEM/ODM supplier, provides over 600 types of window regulators, over 200 types of motors, and complete matching wiring diagrams and technical documents to help OEMs quickly locate and replace faulty components.

2. The company has a complete quality inspection system. All fuses, relays and circuit accessories meet international electrical safety standards, ensuring the reliability and durability of the system after replacement.