87 C4 left headlight motor rotation
 

In the continuing challenge to get the left hand headlight motor to operate correctly, I have purchased a rebuilt motor, & had it bench tested it at the non- chevrolet dealership where I work. It operates correctly on a bench test. NOW, I still need help. I have the 2 part GM service manual, and a fair amount of patience! I don't believe the headlight switch is the issue, but I am asking YOU C4 owners been challenged by the C4 wiring harness, can anyone tell me the approximate location of S131 on page 81-102 of the GM electrical diagnosis service supplement manual? OR, any other areas that are chronic issues on the headlights? :salute:

Need to start with some basic questions: Is your new headlight motor assembly now installed in the car? Did your new motor plug into the harness okay? (Asking about the location of a splice is a puzzling question.) Does your new motor assembly look like this picture, with the manual actuation knob on the bottom of the motor, or does it have the manual actuation knob on the top of the motor?

https://cimg2.ibsrv.net/gimg/www.cor...50db8a0ad1.jpg

:cool:

On my old '87, the manual rotation knob was on the top of the motor. Each headlamp has its' own relay that operates the motor. There is also a 3rd "isolation" relay that changes the polarity of the two headlamp relays which effectively causes the motors to run backwards so that they can retract.

The two headlamp relays are the same so you can exchange them to see if the problem moves to the other headlamp (the isolation relay has fewer wires and a different connector). If you manually raise the headlamps by using the manual knob and then pull out on the headlamp switch, do both headlights come on and stay up? When you push in on the headlamp switch, do both buckets close?

Cruiser, is there any chance you might be mistaken? The '84 - '87 headlight motors should have the manual control knob on the bottom of the motor, like my picture. The '88 - '96's have the knob on the top.

The '88 - '96 electrical circuit is entirely different, and has no relays.

Can we please have someone confirm this information, to eliminate this confusing statement?

:cool:

ok guys,

I REALLY don't know what I did, but the left headlight is working as designed, (at this time!) No guarantees in a week but I will accept it for now. My 1987 motor has the knob at the bottom of the motor.

Sorry for any confusion, but if it works , I will leave it alone.:smash:

AS always, THANKS for the response.
Paul