How to test headlight motor control module?
Thread Starter
Instructor
Joined: Mar 2002
Posts: 118
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From: Teaneck NJ
How to test headlight motor control module?
I have a 1989 style module on my car. Suddenly the headlight motors do not work. When I apply + and - 12 V to them they don't seem to work either. Could the module have failed and burned out both motors? How do you test the module? I don't know at this point whether to replace the module, both motors, or all three.
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Joined: Feb 1999
Posts: 3,504
Likes: 4
From: Mexico Beach FL
I had the module go bad on my '92.
The reason the module went bad was because the wires by the headlight motor got rubbed through by the rotation of the headlight and shorted out. The short destroyed the module.
If your module is like my '92, the thing to remember about it is there are two outputs (one to each headlight motor) and a single input (from the light switch). It is possible for only one output to fail. So, only one headlight motor may be affected.
A quick way to test the motors is to disconnect the connector from the module to each headlight motor and apply ground and power to the appropriate wire to operate the motors. By reversing the polarity on the wires the motor will go in the opposite direction. This way, you can determine if the motors are the problem or the module is the problem.
The module stops the current flow to the motor when the module detects the higher current flow when the motor hits the stop (there are no limit switches in this setup).
You can test the input to the module from the headlight switch with a voltmeter.
Tom Piper
The reason the module went bad was because the wires by the headlight motor got rubbed through by the rotation of the headlight and shorted out. The short destroyed the module.
If your module is like my '92, the thing to remember about it is there are two outputs (one to each headlight motor) and a single input (from the light switch). It is possible for only one output to fail. So, only one headlight motor may be affected.
A quick way to test the motors is to disconnect the connector from the module to each headlight motor and apply ground and power to the appropriate wire to operate the motors. By reversing the polarity on the wires the motor will go in the opposite direction. This way, you can determine if the motors are the problem or the module is the problem.
The module stops the current flow to the motor when the module detects the higher current flow when the motor hits the stop (there are no limit switches in this setup).
You can test the input to the module from the headlight switch with a voltmeter.
Tom Piper
Drifting
Joined: Oct 2003
Posts: 1,594
Likes: 0
From: CALGARY ab
Originally Posted by Tom Piper
I had the module go bad on my '92.
The reason the module went bad was because the wires by the headlight motor got rubbed through by the rotation of the headlight and shorted out. The short destroyed the module.
If your module is like my '92, the thing to remember about it is there are two outputs (one to each headlight motor) and a single input (from the light switch). It is possible for only one output to fail. So, only one headlight motor may be affected.
A quick way to test the motors is to disconnect the connector from the module to each headlight motor and apply ground and power to the appropriate wire to operate the motors. By reversing the polarity on the wires the motor will go in the opposite direction. This way, you can determine if the motors are the problem or the module is the problem.
The module stops the current flow to the motor when the module detects the higher current flow when the motor hits the stop (there are no limit switches in this setup).
You can test the input to the module from the headlight switch with a voltmeter.
Tom Piper
The reason the module went bad was because the wires by the headlight motor got rubbed through by the rotation of the headlight and shorted out. The short destroyed the module.
If your module is like my '92, the thing to remember about it is there are two outputs (one to each headlight motor) and a single input (from the light switch). It is possible for only one output to fail. So, only one headlight motor may be affected.
A quick way to test the motors is to disconnect the connector from the module to each headlight motor and apply ground and power to the appropriate wire to operate the motors. By reversing the polarity on the wires the motor will go in the opposite direction. This way, you can determine if the motors are the problem or the module is the problem.
The module stops the current flow to the motor when the module detects the higher current flow when the motor hits the stop (there are no limit switches in this setup).
You can test the input to the module from the headlight switch with a voltmeter.
Tom Piper
tim 87.. i have a spare if you need one
Thread Starter
Instructor
Joined: Mar 2002
Posts: 118
Likes: 0
From: Teaneck NJ
Thanks for your replies. At this point I'm thinking that the module went bad and fried both motors because it didn't let off the power. I don't have any other explanation why both would fail at the same time and not work when I apply power directly to them. I'll check them again as you suggest Tom Piper. Thanks for your offer korvettte4u. Maybe I'll get back in touch.
Drifting
Joined: Oct 2003
Posts: 1,594
Likes: 0
From: CALGARY ab
Originally Posted by tim87
Thanks for your replies. At this point I'm thinking that the module went bad and fried both motors because it didn't let off the power. I don't have any other explanation why both would fail at the same time and not work when I apply power directly to them. I'll check them again as you suggest Tom Piper. Thanks for your offer korvettte4u. Maybe I'll get back in touch.
also check tech section for repair to motors,,,
anytime thanks
Safety Car
Joined: Nov 2002
Posts: 4,394
Likes: 6
From: Melbourne FL
More great information.
I'm currently trying to diagnose why after replacing one headlight motor I have one light up and the other in the down position!
I'm currently trying to diagnose why after replacing one headlight motor I have one light up and the other in the down position!
Last edited by Z06ufgrad2002; Nov 13, 2024 at 06:33 PM.
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From: Melbourne FL
