Testing for Bad Headlight Motor or Module
Thread Starter
TECH Apprentice
Joined: Mar 2011
Posts: 324
Likes: 25
From: Waterford, MI
Testing for Bad Headlight Motor or Module I've read a bunch of the posts about this and here is where I am at. Passenger side does not move at all, driver side works perfectly. I have both high and low beam lights on the pass side. Manually moves without issue. The connector is quite corroded so I cut the 2 wires for the motor on either side and hard wired them together for testing (will replace the whole connector later). Still nothing. I put a volt meter on the body side wire ends and turned on the lights, saw not even a volt on the circuit so I assume it is likely the control module. But, when I did this on the driver side just to make sure, I saw the same voltage. Will I only read 12 volts if the circuit detects a load?
Another thing that confuses me is I hooked the motor up to the battery and it did nothing, so I also thought maybe the motor is bad. I got a new one and did the same thing with that, it does not cycle either. What am I missing here?
Another thing that confuses me is I hooked the motor up to the battery and it did nothing, so I also thought maybe the motor is bad. I got a new one and did the same thing with that, it does not cycle either. What am I missing here?
Joined: Nov 2003
Posts: 11,330
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
I would have said check the RH HDLP DR fuse in the junction box on the left fender well under the hood (there are separate left and right fuses) but I assume that you bypassed the fuse block when you connected to the battery. I am at a loss to see how you could hook the motor directly to the battery, have it not work, and it not be the motor itself. Doing that eliminates all wiring issues so it would seem that it would have to be the motor.
Thread Starter
TECH Apprentice
Joined: Mar 2011
Posts: 324
Likes: 25
From: Waterford, MI
Yes I did run the motor wires straight to the battery, which did not cycle it, so I figured it was the motor. When I got a replacement motor and it did the same thing hooked to battery, while I can't rule out a bad replacement motor, seems odd that I would get same results.
I'm also unclear on how the voltage reads at the connector on the body side, since I couldn't get hardly any voltage to read on either side, does it need to see a load in order to read a voltage? Like I'd have to back probe the connector when running the motor to see anything? Because the driver side works fine, but when I pulled the connector, hooked my meter up to it, turned the headlight switch on, i got less than a volt. Yet that side still cycles the motor. I want to make sure I don't have multiple issues going on here.
I'm also unclear on how the voltage reads at the connector on the body side, since I couldn't get hardly any voltage to read on either side, does it need to see a load in order to read a voltage? Like I'd have to back probe the connector when running the motor to see anything? Because the driver side works fine, but when I pulled the connector, hooked my meter up to it, turned the headlight switch on, i got less than a volt. Yet that side still cycles the motor. I want to make sure I don't have multiple issues going on here.
Joined: Nov 2003
Posts: 11,330
Likes: 346
From: Jacksonville, FL (originally from Toronto Canada)
The output from the module to the headlamp doors is reversible polarity using a PWM signal and a solid state signal monitor for control. Testing would have to be done with the doors connected because the signal monitor won't allow full output without the load.
