I'll try to keep this brief (somehow!). My headlight doors do not open/close unless the engine is running, so I was trying to find the fault. I didn't find it, but I found this instead: When I disconnected the small vacuum pipes (with the "t" piece) from the top of the headlight relays then both lights popped up (engine running). They both start to lift at the same time, then the passenger side almost stops while the drivers one shoots open with a loud "clack" & then the passenger side gently finishes opening about 1 sec later, no "clack". If I connect the small vacuum pipe to each relay in turn, blocking/unblocking the other end of the "T", then each light opens/closes in the same way. The passenger headlight door also wobbles when driving over bumpy roads, whereas the drivers side one is rigid. The question is, which headlight door is operating correctly? Should there be a loud "clack" when they open? And how do you get them to open/close in unison?
Cheers
Paul

 

guess I'll take the first whack at this.

1. The headlights are vacuum operated and the best working systems will not open the doors after a couple of hours of the engine turned off (vacuum has leaked out). Marginal systems will not work at all without the engine running.

2. My doors open and lock in place. I guess you could call it a "clack". There are adjustments to the doors that adjust how far they open and then lock.

It sounds like you may have a small vacuum leak and/or the passenger side acuator is leaking, not pulling that door up as fast.

As to the passenger side wobbles, it may need adjustment to lock open.

Hope this helps.

Terry

 

Thanks Terry,
That's stopped me worrying. Usually when things go clack/thwack/clunk they are either designed to, or are about to break in the most expensive way possible
Cheers

 

If you can grab the door when open and it wiggles around, you may need to replace the headlight bearing(s). These are actually a nylon bushing inside of a metal carrier and held on by 3 bolts. The outboard ones are "challenging" to get at, so I hope you don't have this trouble. Any excessive play will be obvious.

The adjustments for how much the door opens are evident, although you may have to remove the grill or valence or other stuff to see better. One of mine was not hitting the design stop and broke part of the housing. It looks like they can go "over center" also making it difficult if not impossible to get them closed.

good luck!

 

Thanks Frank,
The more I read up on these headlight doors, the more paranoid I'm getting about touching them! :eek:
Maybe I'll just put this job further down the "to do" list and fit my new factory alloys, sort out the air con, fix the trans leak, re-core the rad, check that the ECM is going into closed loop....... :lol:
Would reserving an entire day sound about right for sorting out the headlights?
Paul

 

Just FYI - I've had mine for many years and one light always seems to beat the other into the fully open position...

 

Headlights aren't that difficult. The worst part is getting the springs back inplace without cussing so loud to embarass the neighbors :cuss

The headlights in my 1978 are exactly as your lights sound. however, the passenger side locks as well, but I have some play in the bushing near the center of the hood. The adjustments for door open height are 3 bolts in slots on the headlight assembly. You will need to remove the lower 2 springs, once they are removed, you will see the bolts. There is also a stop screw on the outboard "arm" of the headlight assembly. Adjust this so it contacts the fiberglass when the light is open. This helps reduce "bounce" and when set correctly makes a firm lock in place, not so much a loud "clack".

Jeff

 

Thanks for all the help. I'm not too bothered about them not opening/closing at the same speed, it's just the way one goes clack/crack/clunk & the other doesn't. The clack/clunk is loud enough to make pedestrians stop & look over (the ones that aren't already ogling the car ;) that is!) so I'll have a fiddle over the weekend.
Cheers
Paul

 

Hey, from what I have read on the forum, if your headlights open and close, then count your blessings.

 

UKPaul: I thought I too had bad bearings/bushings on my driver's side headlight door since it jiggled when driving at night, however upon closer(finally) investigation, I discovered a broken and partially missing support bracket, so I fashioned one (call me Bubba), installed it, and no more 'jiggle', and didn't cost me anything, but about an hour's time. Something you might want to check out in your vette.

 

John, thanks for the tip. The headlights have been pushed down the queue due to my lockup torque converter not locking up. But, trying to find the TCC problem has led me to fix a check engine light problem that I'd given up all hope of fixing! Maybe if I try to sort out the lights then I'll find the fix for the TCC?! ;)
Virtue4u, yes I've got that impression as well!
Thanks
Paul

 

I feel your pain with the check engine light. I followed the shop manual and determined I had a bad ECM. I bought a replacement off of ebay that the guy said was working when it came out (only $30 so no big loss) and still no check engine light :cuss If you don't already have a Helm manual, get one it has about 100 pages just on the ECM :yesnod:

 

Stickboy,
Pain describes it very well. I've got the shop manual which is not bad, although it does reference another manual for more info on the ECM :rolleyes: Is there an ISBN number for the Helm manual? Where did you get it from? As far as I know, I'm the only person in this country still running an ECM on an '81, so I need all the help that I can get
This is probably an obvious question (its not "have you checked the bulb"!), does the battery warning light come on when you turn the ignition on? I had the same problem last night, no check engine light, thought I'd blown my ECM while looking for the TCC problem :cuss so I've just been through all the checks for no check engine light!
Cheers
Paul

 

As far as my headlights on my 71, they clank and clunk when opening. A friend of mine just bought a 75 and his driver side light goes up faster that the passenger light just as mine does. They also clank and clunk. I WD-40'd the bearings and used white grease and the clank and clunk got less noticable My owners manual says that the light system can be raised and lowered a few times with the engine off. Of course mine won't. With 30 year old hoses I don't think any 71's will. I am with virtu4u..........if they go up and down, turn on and off and you have high beams and low beams then you are good to go.
John


[Modified by theandies, 4:15 PM 9/5/2001]

 

Paul,
My helm's manual is a shop manual. I bought mine off of ebay but you can order them at http://www.helminc.com/helm/homepage.asp. Yes, my batery low light come on, does that mean anything? My vette is a manual so I don't have all the TCC stuff. I followed the manual for diagnosing the "No Check Engine light" too. Weird thing is if you check voltage where the light plugs into the console, the contact were you should get a ground through the ECM, I get +6 volts.

 

stickboy,
Thanks for the link. It's a pity that your battery low light comes on, thought I might have been able to help you out there. Mine didn't & the manual said "check fuse". The fuse was OK but I found a bad connector which was causing the problems. Obviously it won't be the case on yours.
Know the feeling with the +6v - I did the TCC check where you connect a test light between the TCC test connector & ground. The light did the complete opposite of what the manual said it should do :crazy: The next test pointed to an open in the wire to the TCC test connector, but it buzzes through OK. Electrics, weird, very weird. Have you checked all the earth points (easier said then done!). I've seen problems like that due to bad earths. With the ign on, connect a voltmeter terminal to the wire going to the earth, with the other terminal connected to earth. You shouldn't get any voltage shown across a good earth.
Also, have you tried swapping the PROM from your old ECM into the new one? We're always blowing PROMS at work if there is a problem in a circuit board (they are very unforgiving when things aren't quite right). Electrical problems aren't good at the best of times, but in these C3's it is a whole lot worse coz it's so hard to get at everthing. It doesn't help when somebody else has modified it & none of the colour coding matches up :mad
I wish you luck!
Paul

 

paul, I didn't check the grounds yet, but that is a good idea. Unfortuanately I only have one PROM, the new computer I got is a custom job and doesn't use a Prom. But I am experiencing the exact same things no matter which ECM is in, so I am hoping it is a problem somewhere else.