chll69

So i have been searching the forums for an answer and cant find one so here i am.
I have an 86 coupe and my right headlight had stopped working so i opened it up and saw that the little circuit board piece in the casing that attaches the wires had a contact that broke off, so i soldered it and motor works. Before plugging it all back up i just plugged the connectors to make sure it would spin the motor open and close and it did. NOW here is where i have my problem. After seeing that it does turn when connected i then bolted the motor onto the car as it should be and the motor snaps the headlight into the full closed position, great and all but when i put the headlights on it wont open the headlight. I went through the process of taking the motor off a the car to test is without being attached to the car and it spins open and closed! So my problem still remains, when attached to the car it will not open, does anyone know what the problem could be?!?!? thanks!:

jeffp1167

If the housings contact anything while opening or closing it will trip the relays and make the motors stop.

chll69

I am not quite sure i understand what you are saying? the headlight itself contacts the hood by the bumper piece and stops it from closing any further because it it fully shut, but opening it is where nothing moves, the motor does not even try to rotate

GREGGPENN

Headlights usually fail due to stripped gears or problems with the relay circuit. IIRC, there's a sticky at the top of this forum detailing the issues you should check.

Gears need to be replaced -- if stripped.

The power circuit runs off a timer and resistance. When the headlight rotates and hits the "stop", circuit resistance goes up and shuts it off. If there's mechanical resisant (to the rotation), the circuit could shut off immediately. If neither occurs (because the gears are stripped), a timer kills the circuit after 10-15 seconds.

From these basic facts, it should lead your diagnosis.

8valve

If your 86 is the same as my 87, there is no electronic control on headlights opening and closing. The motor shaft is spring loaded,
when the headlight reaches the end of travel (either open or closed) the motor shaft tightens and actually moves the shaft a small bit. Under the shaft you will see a small plastic slider. There is two mechanical contacts that are activated by the plastic piece moving in either direction. These contacts open and close depending on the state of the headlight (open or closed).

Look on your motor assembly. Look on the end with manual crank ****. See the large spring ? The spring is tricky to get in the right groove so the shaft can move either direction and operate the mechanical contacts. If the spring is not in the groove, only one contact can be activated.

With the motor open, push an pull on the manual operation ****. You will see the motor shaft move roughly .125" in either direction. While doing this look under the motor shaft and be sure the plastic piece is contacting/ moving the mechanical contacts.

My bet is you do not have the large spring properly in the groove and thus the motor shaft can only move one direction.

I just went thru this exercise with my right headlight.

8Valve

GREGGPENN

Well, Ain't that a kick-in-the-pants! I did not know earlier C4's had a different headlight mechanism.

Ray Quayle

Don't feel bad, Gregg. Many don't know this as many early C4s have been updated to the newer design. Some will even argue because their early C4 has the headlight module and works on current that they are all like that. Paul (8valve) sounds like he's done a few, good explanation!

LaVidaLoca

Here is the diagrams for the two headlight systems on C4s:




Note that on the pre 88 style that the DOWN relay is common to the two sides. The UP function has a relay for each side so if one side goes up but not the other it could be a relay. Could also be the internal contact for the UP function also.

Try swapping the relays. They are the same.

chll69

thanks everyone for your help! I figured it out! it was a combination of things. One the Spring and two the the round magnet has to be placed in correctly and i had it in just not 100% correct! headlights work great now!!

8valve

Super ! Well done

8Valve