Here's a link to the original thread I posted several days ago. http://forums.corvetteforum.com/show....php?t=1776337

Well, I installed the new "headlight control module" but, it didn't solve the problem. The right side headlight still doesn't go up on the first try. I have to manually turn the motor **** a few turns and then the headlight will spin around. After that, both headlights operate fine until the Vette is parked for an hour or so.

I cleaned and checked all connections and all power wires are receiving 12 volts. Everything seems to operate fine once I turn the right side motor **** a little. I already replaced the bushings and plastic gears in both motors about a year ago.

Both headlights always turn on. I don't know what else to check for. My daily routine before I leave for work is, I open the hood and turn the right side **** a few turns then when I leave work at night, I turn the headlight switch and both headlights rotate up everytime.

Any guesses? Thanks for your help.

 

First, let's troubleshoot the wiring leading to the Headlight Control Module:

Disconnect the large connector to the Headlight Control Module. The larger one has 5 wires: yellow (A), red (B), white (C), black (D), red (E). B and E (both red) must carry 12V at all times or the module doesn't get power. B is power to the left motor, E for the right motor. So if one side doesn't work and there is no power on the respective wire, check and replace fusible links or wiring.

D is the ground for the headlight control module. This wire must be continuous with ground at all times.

Yellow (A) and White (C) are signal wires from the headlight switch. White tells the module the headlights are "OFF". Yellow is the power signal that tells the module to activate the motors as the headlights are "on".

Testing the system:

With a test light to ground probe B and E (red wires) at the 5 pin connector that leads to the Headlight control module. Both should have power at all times. Then connect the test light to the + side of the battery and probe terminal D (black wire) Test light should light up.

Hook the test light back to the negative side of the battery
With the headlight switch "OFF":

probe C (white wire) on the 5 pin conntector to the headlight control module. Test light should light up.

Probe A (yellow wire) on the 5 pin connector at the headlight control module. Test light should be off.

Now turn the headlight switch "ON":

Probe C (white wire) on the 5 pin conntector to the headlight control module. Test light should be off.

Probe A (yellow wire) on the 5 pin connector at the headlight control module. Test light should be on.

Perform these test and post your findings.

 

Hello- BTDT... Even though you did 'em last year, it really sounds like the bushings on that side are not grabbing. They mostly always close, even when bad. It's in the opening that they take the strain.....I've yet to see anybody that really had bad gears or an electrical problem. It's always them crummy little bushings....What are those things made of anyway? Some kind of gel pack or something??? Very marginal/cheap type parts at best...............
I'm sure you know this, if you want to try a different motor/mechanism (you'll have to scrounge because everybody grabs 'em up quick when they come in to the junk yards) The Pontiac Fiero used the same mechanism......

 

That is exactly what I figure his problem is but at this point he's already thrown parts at it to no avail so if he does a good, thorough diagnostic of the system he can pinpoint the exact problem and fix it right. I was just looking at Fiero motors on E-bay and while the mechanical drive mechanism appears to be different than the Corvettes the electric motor appears to be exactly the same.

 

Thanks for the replys.

I already checked the connectors at the control module and headlight motor connector for 12 volt power as described. Everything checked out fine.

This is an intermittent problem, for example: last night I went out to dinner with my wife and both headlights rotated up and down fine for the entire trip. When I arrived home, I decided to go back in the garage an hour later to check the headlight operation and the right headlight failed to rotate up. This morning I decided to check the headlights again, and both operated fine.

It doesn't sound like the bushing because the motor doesn't keep running and the headlight rotates up and down smoothly when it does work (I'm not ruling it out though).

Here's a summary of what I know so, far:

1) Both control module connectors, headlight motor connectors, fusible links and relays all receive 12 volt power.

2) Both headlights turn on and off.

3) There is no noise from the headlight motors.

4) Both headlights operate smoothly and quietly when they do work.

Would a weak battery have anything to do with this? The battery is a 3 year old Ac Delco which recently died while checking this headlight problem and I also, installed a CS-144 140 amp alternator last year. After I recharged the battery, the voltage is 12.3 engine off, 13.8 engine on.

Any thoughts? Thanks again

 

If you haven't already tested the wiring at the headlight motor try the following: unplug the two wire connector (dark green/grey wires) leading to the headlight assembly. Ignition on. One side of test light to ground. Probe both wires with the Headlight switch "off". One wire (can't remember which) should have power. have someone switch the headlight switch ON and OFF several times. Is the test light switched on and off consistently with the switching of the switch? Do the same for the other wire. This will eliminate the possibility of the problem being an intermittent short to the headlight motor. If all checks out check the wiring from the two wire connector to the headlight motor itself. If all looks good the problem lies in the motor itself.

One thing you could try that comes to mind is open the hood, turn on the headlights and cycle them trough until the right one stops working. Then lightly tap the motor with the handle of a screwdriver, hammer etc. See if that gets the headlight to operate. That would mean something (a brush, or the motor) has an intermittent short.

FYI parts are available for the motors, and the motors themselves are the same as a '87/'88 Fiero and '93 - '02 Firebird unit so if you need to find parts you may be able to avoid the Corvette tax by buying Fiero headlight motor parts.

Note that only the motor assembly is the same as the Fiero and Firebird. The drive mechanism the motor attaches to is Corvette specific. It sounds like your problem, if it isn't the wiring leading to the headlight motors, is in the motor itself not the drive mechanism.

 

I just tested the dark green and grey motor wires as you suggested above and both wires lit up the test probe light on both left and right headlight motors.

With the ignition on, test probe on the dark green wire, I turned the headlight switch on and while the headlight rotated up the test probe light went out until the headlight was up then it lit back up. This happened on both the headlights.

I noticed that 100% of the time when I just turn the right headlight **** a little before I turn the headlight switch on, the headlights Always operate fine.

I think the motor is having an intermittent switching problem.

 

Hi again- Maybe my bad...
I will be the very first to acknowledge that as much as I have learned about these cars (not always because I wanted to, if you catch my drift) I certainly still know nothing! I knew about the Fiero motors because I ran into a guy at a junk yard about six years ago that was pulling them saying he was making some money by cleaning them up and re-selling them for Corvettes. A GM friend (a true automotive wizard) who knows many of the more obscure mechanics about Cadillac and Corvettes later told me that the mechanism was also the same. Like the rest of us, I guess it's only fair that even he's entitled to be wrong once in awhile?
You say no, I'm okay with that because I personally never checked it out and just took it for fact by the source. Please accept my apologies...:o
Now with that said, it's been my experience in talking with other Vette owners that the motor either works or it doesn't. I'm still thinking it's those crummy bushings new or not...

 

One last thing, does that headlight lock in the open position or can you move it with your hand, even just a little bit? Do you notice it bouncing any as your driving with the lights on? If you can or you do, then I really do think it's the bushings. If not, maybe it is the motor. Another Corvette NIGHTMARE! You will eventually awake from it one way or another. Let us know what you find there on your journey into darkness. I can actually feel your pain (more like PO'd aggravation) many times over for many years now......

 

When the right side headlight opens, it locks into place and they operate normally.

I've been testing this problem most of the weekend and with the suggestions I've received here on the forum, I'm confident the problem is in the motor itself.

 

It would be AWESOME if the entire headlight assembly was the same. I can only say that the motor looks exactly the same from visual inspection. It's entirely possible, and makes sense, that the '87/'88 fiero, '92 - '02 firebird and '87 - up Vette all share the same headlight assembly. From looking at pictures of the Fiero and the vette motors they appear to be visibly different. The motor assembly appears to be the same but the drive mechanism appears different. Next time I'm at the salvage yard I'm going to check it out - it would be very cool if you could use Fiero or Firebird assembles

 

most of the time when there are issues with the later motors it's the Derlin bushings. They are available for $5.99 from Mid America. It would be worth pulling the motor and taking the cover off to check it out before buying a while new motor assembly.

 

Next week, I'm going to order a refurbished motor assembly from Ecklers, since I don't want to take a chance with Fiero motor assemblies not matching.

Before I change the motor, I'll check the bushings. If the bushings are good, I'll install the new motor and I should be good to go.

Thanks everyone for all your help!