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When hooking up the battery...something I have done a lot lately, I hear both headlight motors run for a few seconds, and then they stop. Seems it is mostly the passenger side, but the driver's side a little bit too. They stop running, and then that's that. I had a test light hooked up while diagnosing an alternator short, and the light...kind of somewhat dimly strobes/pulses along with the sound of the headlight motors...just for a few seconds. My '86 has the older style headlight motors, and don't do this. Any idea what's wrong here?
Possibly a bad headlight control module, drivers side fender well toward nose of car looks like the following pict. You can test the light motor itself by running 12 volts to the headlight motor and see if the noise happens that way too.
If the headlights are are in the down/off position and you hear the motors running, that means the gears or (more likely) the round plastic bushings inside the gears are shot. The motor shouldn't be able to spin if the lights are at either end of their travel. I wonder if it's normal for the headlights to attempt to close (or open, if the switch is turned to "On") when battery power is restored? This would be part of an overall reset process. But normally we don't notice it because the motors stop immediately upon sensing mechanical resistance (due to increased current draw, because they are already fully open or closed). I'm just guessing at that, though.
The question comes down to how the control module knows when to stop powering the headlamp motors when they are at either end of their travel. I know that when the bushings are shot, the motors are no longer solidly connected to the doors, and so the motors keep turning even when the doors are fully open or closed. When the bushings are replaced, the motors stop as soon as the doors reach either end of travel.
Last edited by MatthewMiller; 04-12-2018 at 09:55 AM.
If the headlights are are in the down/off position and you hear the motors running, that means the gears or (more likely) the round plastic bushings inside the gears are shot.
Since the headlamps/controller etc are an always 'powered' device what you're hearing is to be considered normal. Bad bushings? Maybe but I'd think it's just the controller resetting itself during the connection.
If the headlights are are in the down/off position and you hear the motors running, that means the gears or (more likely) the round plastic bushings inside the gears are shot.
That wasn't my case, that's why running 12 volts to the motors will tell if the problem is with the gears or module...the FSM indicates doing this as a troubleshooting step.
For me it turned out to be the headlight module. The strange thing is running 12 volts directly allowed the lights to open/close and stop the motor once either fully open or fully close...so I'm not even really sure what the function of the headlight module is.
Possibly a bad headlight control module, drivers side fender well toward nose of car looks like the following pict. You can test the light motor itself by running 12 volts to the headlight motor and see if the noise happens that way too.
Thank you! Thanks for mentioning the location...it helps!
If the headlights are are in the down/off position and you hear the motors running, that means the gears or (more likely) the round plastic bushings inside the gears are shot. The motor shouldn't be able to spin if the lights are at either end of their travel. I wonder if it's normal for the headlights to attempt to close (or open, if the switch is turned to "On") when battery power is restored? This would be part of an overall reset process. But normally we don't notice it because the motors stop immediately upon sensing mechanical resistance (due to increased current draw, because they are already fully open or closed). I'm just guessing at that, though.
The question comes down to how the control module knows when to stop powering the headlamp motors when they are at either end of their travel. I know that when the bushings are shot, the motors are no longer solidly connected to the doors, and so the motors keep turning even when the doors are fully open or closed. When the bushings are replaced, the motors stop as soon as the doors reach either end of travel.
Thanks...I am kind of wondering if it is some sort of reset process too. It only happens when I reconnect the battery. Never does it when just starting the car, etc. Anyone had their battery disconnected lately to know? Maybe I can make a video...
Since the headlamps/controller etc are an always 'powered' device what you're hearing is to be considered normal. Bad bushings? Maybe but I'd think it's just the controller resetting itself during the connection.
**Headlamps require 'no key' for operation.
Makes sense...thanks. Guess I will see if I have any problems now that the battery is connected. Hasn't happened since...
That wasn't my case, that's why running 12 volts to the motors will tell if the problem is with the gears or module...the FSM indicates doing this as a troubleshooting step.
For me it turned out to be the headlight module. The strange thing is running 12 volts directly allowed the lights to open/close and stop the motor once either fully open or fully close...so I'm not even really sure what the function of the headlight module is.
I will probably pick one up at the salvage yard in case...thanks!
I've run into this problem recently, replacing the gears cleared the issue.
It does have me wondering, since my '86 never does anything like that...though the motors are different. Maybe I'll try rebuilding them. Anyone know where a good write-up is, and maybe the best place to get a rebuild kit with gears and bushings?
I will probably pick one up at the salvage yard in case...thanks!
I have one from the 'Vette Kart project if you decide that you need one.
Also w/the gears; you can save time and a few bucks by simply filling the ID of the gear w/epoxy. I did that to my '92 years and years ago...still working beautifully.
I have one from the 'Vette Kart project if you decide that you need one.
Also w/the gears; you can save time and a few bucks by simply filling the ID of the gear w/epoxy. I did that to my '92 years and years ago...still working beautifully.
Okay, if it turns out I need one...any idea how much? What's the "ID"?
04-12-2018, 04:29 AM
Not your typical headlight motor question...
