Help! Headlight problem---Need Help

[Murf]

Sorry if this is long, want to be thorough. The left headlight (drivers side) will not open when the switch is pulled. Right side functions ok. Both headlights turn on. 88, so no relays. Has control module. Bushings in both headlight motors replaced about 2 years ago. So far, I have replaced control module and headlight switch. No luck. Headlight motor will open and close if I jumper direct from battery to plug from module by reversing polarity, so wiring seems ok. If I turn lights on and crank left one open, it will close when switch is turned off. Voltage into module is ok. Both reds and white have voltage with switch off. Both reds and yellow wire have voltage with switch on. If i unplug right headlight and jumper from right harness to left, the door will function both ways when turning switch on and off. I'm stumped. Want to sell car, but need to solve this first. Any help greatly appreciated.

Thanks, Murf

 

[gmhowe]

Might sound stupid but my 85 does the same thing sometimes, I just go out and give it a good wacking with my fist and it opens up fine.
Gordon

 

[tonylong]

Might sound stupid but my 85 does the same thing sometimes, I just go out and give it a good wacking with my fist and it opens up fine.
Gordon

Ahh the Fist. My favorite tool. Usually gets it's attention.
Especially when it realizes that after the fist comes the Ballpeen Hammer, another favorite tool. lol

 

[Murf]

Still looking for some answers. Anybody????

 

[gmjunkie]

My guess is you Have a BAD Module!!! I have 3-4 modules here that are Bad in the same way,just different sides!!

 

[tonylong]

Is it possible to switch components between left and right assemblies? If the problem moves then that was the bad component. Just trying to suggest a debugging method.

 

[Murf]

Junk,

Got a used module, did the same thing. Bought a new one, same result. Could I have a bad connection when I plug it in? Harness seems ok. If I put voltage to plug coming from module, light will open. Reverse it and it closes. Does same for both sides. When plugged in, right side is ok, left side won't work.

Tony,

Unplugged both harnesses going to lights. Ran jumper from right (working ) light to left light. Pull switch and it opens. Push switch and it closes.

 

[tonylong]

Junk,

Got a used module, did the same thing. Bought a new one, same result. Could I have a bad connection when I plug it in? Harness seems ok. If I put voltage to plug coming from module, light will open. Reverse it and it closes. Does same for both sides. When plugged in, right side is ok, left side won't work.

Tony,

Unplugged both harnesses going to lights. Ran jumper from right (working ) light to left light. Pull switch and it opens. Push switch and it closes.

This sure sounds like a wiring issue. If the units open under any conditions then the module should be OK.
Before getting too "inventive" I'd recheck all connectors,
unplug and re-plug 'em all. Be sure they're connected firmly, and that the terminals are clean, wouldn't hurt to clean them with alcohol just to be sure.
See what happens.

 

[gmjunkie]

Junk,

Got a used module, did the same thing. Bought a new one, same result. Could I have a bad connection when I plug it in? Harness seems ok. If I put voltage to plug coming from module, light will open. Reverse it and it closes. Does same for both sides. When plugged in, right side is ok, left side won't work.

I suppose you could be getting a bad connection on 1 pin,but I would think it would get a connection sometime as many times as you've had it plugged,unplugged and plugged back in again!!

 

[onedef92]

Are you sure the offending light isn't getting snagged on an underhood hose? I've seen one of the headlight assemblies getting bound like this and not opening properly.

 

[Murf]

Not getting snagged. If I bypass wiring and apply power to harness terminals, light will open and close.

 

[tonylong]

Not getting snagged. If I bypass wiring and apply power to harness terminals, light will open and close.

Where on the harness? Near the lamp, or further in? Try moving the test connection further and further away until it won't work. Just gotta do some debugging.

 

[Murf]

Tony, unplugged harness where it comes out of module. Applied power there. Everything going into module checks out. Module is brand new, so is switch. Just replaced both. Thinking I might have a connection problem when it is plugged into module.

 

[tonylong]

I'm assuming that the "module" is right there by the headlight housing. It's pouring rain here so I'm not gonna go out and take a look at my 89. If module is out by headlignt, can you go further upstream and try jumpering there? If all components are new, it's gotta be either the wiring itself or connections.
What if you jumpered the feeds from the "good" headlight to the "bad" one. It that works, well f-it, just let it stay jumpered. =] Spend your time driving, not fixing. =]

 

[luvmyc4]

Mmhmm

Might sound stupid but my 85 does the same thing sometimes, I just go out and give it a good wacking with my fist and it opens up fine.
Gordon

Worked 4 me for 2 weeks then traced prob 2 switch in dash.only i did a slight whacking lol.

 

[garyg]

headlight doesn't open

I have a 1988 C4, most likely the small bushings in the motor drive have crumbled. This happens with age. I replaced the bushings in both headlights which takes about three hours. The three Delrin bushings cost about $9.00 a set and are available from Mid America. I strongly recommend removing the complete headlight unit and working on a table. There are step by step instructions with pictures available at corvettefever.com/howto/33098/photo_12.html site. Also, do both headlights.