The LH headlight motor quit working on my 94 C4. I made an assumption that it was motor failure and purchased a rebuilt motor. The rebuilt motor doesn't work either. I checked the voltage to the light....which I should have done in the first place...and the motor gets 12 volts when the switch is in the 'on' position, and nothing in the off position. The RH headlight motor, which works fine, has 12 volts of power in both on/off positions of the switch. So.....am I looking at a bad headlight door modulator? Is there supposed to be power present to the motor with the switch in both positions?

 

Welcome to the forum.

There are two major issues with the headlamps. Sacrificial pellets in the gear fail and/or the headlamp control module fails.

The first one is an $8 fix.

After five months, I'm still struggling with the LH side sticking.

There are many threads about this topic, as it is experienced by at least 60 percent of C4 owners.

Here's one. https://www.corvetteforum.com/forums...eadlights.html

And this: https://www.corvetteforum.com/forums...ht-issues.html

Of course, now you are eligible to vote here! https://www.corvetteforum.com/forums...gone-limp.html

Good luck

 

You would highly benefit from the purchase of a FSM (Field Service Manual) for your year. You can get them on DVD from eBay and other sources.
Also watch several You Tube videos on this repair - there are a lot of them out there (some of them suck).
I will say it again, "Don't guess - diagnose first".
The FSM will pay for itself many times over if you can do your own work.
http://www.ebay.com/itm/1994-Chevrol...VWu8Ay&vxp=mtr

 

AS written in a previous post. Obtaining a FACTORY SERVICE MANUAL will be a very worth while investment you make for this Corvette.

YES...POWER is at the motor at both positions....BECAUSE the power and ground are switching back and forth when you use the switch.

AND...when you get the FSM...it will go in very good detail on what to check.

YES...you can have a bad controller for your headlight motors....which SHOULD BE located in front of the driver side tire wheel well liner...right under where the headlight housing would be with the hood closed. Black square box with TWO electrical connectors going to it.

DUB

 

Change the pucks first 6 bucks for both sides off ebay.

 

Also available locally at any auto parts store under the "help" section. They are labelled for use in Ford window motors.

Because you bought rebuilt, I kinda think this is a waste of time. No offense antfarmer2, but something else is stopping this headlamp. There are already new pellets in your rebuilt motor.

The Factory (Field?!?) Service Manual everyone is so keen to see you purchase has very detailed step by step troubleshooting sections. But I waited until after tossing a bunch of money at the problem before buying mine.

It looks like mine was being stopped by loose junk hanging around near the spinning headlamp. Tentatively fixed.

Good luck with this vexing little gotcha.

 

Instead of assuming or buying parts, I would disconnect the motor not working, take off the six nuts, carry it to the other side and plug it into that connector. Be very careful operating it,you can catch your fingers or damage the paint. You'd know very quickly if it's in the motor/gear assy, or in the controller or connector.

 

Actually...why do all that extra work o removing something. Knowing that the two-wire motor for this Corvette requires power and ground. A person can simply disconnect the motor connector and apply 12 volts to one terminal and then a ground to the other and see if the motor works...if it does not...then switch the power and ground at the terminals.

THEN if the motor failed both of these tests.....simple turn the **** on the motor a little bit and test it again. This is because some motors can have a burnt spot on the armature and the brushes are not making good contact...and turning the motor **** a little will move the armature and the motor MAY work.
Simple as that.

And IF the one side is working PERFECT,,,the 'bad ' side is wired the same way....So it is easy with a volt meter to see if the SAME colored wire when the headlight switch is pulled is getting power on the GOOD side is getting power on the bad side....and then also verify the GROUND. Test it with the headlight switch pulled and also pushed in.

DUB

 

I've spent my whole life in electronics, and I'd still pull it and move it over to eliminate assumptions. If it does the same thing on both sides, you'll know it's in the motor or gears. It takes less time to take it out than to do all the measurements and compare wire colors and voltages. I'm not saying you should, I'm saying I would.

 

Like someone said earlier, the FSM will step you through troubleshooting with a flow chart, if you can't pin down what's missing on yours.

 

THANKS AGAIN GUYS....YOU ALL GAVE ME SOME GREAT INPUT. THE FIRST THING I'M GOING TO DO IS GET A FSM...THEN I'LL TACKLE THE PROBLEM. I GOT THINGS OUT OF ORDER.

 

TRUST ME...the time to use a volt meter and check is less time than it would take to remove and reinstall and adjust a headlight housing. the only reason I know this is because I do BOTH and I know which is faster. Using a voltmeter and jumper wires is MUCH faster.

Obviously I have not spent my whole life in electronics...but I HAVE spent a lot of time dealing with electronics on these Corvettes....and often times what GM tells me to do...using jumper wires and a volt meter will tell you all you need to know. Heck...even the service manual does not tell you to remove the motor and take it to the side that is working...because you do not have to.

BUT...a person can do whatever they want. Just giving input from someone who works on them a lot.

All I know is that I have dealt with many headlight problems and I do not have time taking out parts that I can simply test while they are still installed. And I can replace the headlgith motor also WITHOUT removing the entire assembly...that way the headlight door is still were it was when it came into my shop. I do it quite often when I service the pellets in the 2 -wire headlight motors or the gears in the three-wire motors.

"WORK SMART...NOT HARD" is what I say.

DUB

 

I tried very hard in both my last two posts to make it clear that I was saying how I WOULD verify the problem is definitely in either the motor/gear ***-y or the controller. I didn't say either you or clearcreek should. Not everyone knows how to use a meter or diagnose what it means when they do or don't get a voltage. I merely offered an alternative that I, again I, would use as a positive diagnosis as to which way to go with the troubleshooting. Didn't mean to get you riled up over an alternative check.

 

NOT riled up...sorry if I came across that way....DID NOT mean to do that...AND I got what you were 'saying'. And I wrote in the 3rd paragraph of my previous post. BUT...a person can do whatever they want. Just giving input from someone who works on them a lot.

If a person does not know how to use a voltmeter...or use jumper wires.....then they should not be messing with their car. That is my opinion on that because that is what causes me to have to go back in on some previous repairs by people who should not have touched anything at all and backtrack on what they did and repair is all correctly again. Decades of repairing Corvettes..I have seen my fair share of poor attempts where someone tried to fix something themselves. And I can not count the number of 1984-1996 Corvettes that someone serviced the headlight gears or pellets ( for example) and did not get the headlight housing in correctly adjusted and the wiring harness correctly secured and they are scrubbing paint or all jacked-up looking. Not everybody has an eye for the fine details. Just get it in and fixed is as far as they often times go. Only 'speaking' from what I deal with.

I KNOW people can learn and repair their own cars...and I am all for that. But if the person does not want to acquire the tools or skill set and knowledge to repair the specific problem that they have...I see a possible problem just waiting to happen. Kinda like swinging at a Pinata...and obviously being blindfolded.

Like I wrote...they can do it how ever they feel like it as far as I am concerned. I can only comment from the perspective that I have come to rely on.

ALL IS GOOD as far as I am concerned.

DUB