I did try a search but couldnt find a definitive answer.
I have an 87 GTA and I am trying to sort out the mess the PO left on the Front Lights loom.


I need to know where the relays should be located however looking at the service manual is not of great help as multiple digrams contradict eachother.


Can you let me know the proper locations of these relays perhaps someone has some photos to make it easier?
- Headlamp Isolation Relay
- 2x Headlamp Actuator Relays
- Fog Lamp relay


Really appreciate anyone's feedback..

 

1987 was the first year for two wire headlight motors. That system uses the headlight module instead of all the relays and switching motors, etc.

The module is on the firewall next to the brake booster and wiper motor. Black box with two weatherpak connectors, says "GUIDE" on it. Slides into a steel bracket bolted to the firewall. It's a non serviceable part.

GM Service Manual will tell you how to troubleshoot the system, but generally eliminate everything but the box, then if the problem persists, it's the box. Even if it's not the box, start keeping an eye out for the boxes. It doesn't hurt to have an extra on hand nearly as much as buying an overpriced box when one or both headlights go wonky.

 

My system uses the 3 relay system with Isolation Relay to reverse polarity. Either the loom is not original or they were still using the 3 relay setup.


I cannot find the 87 service manual. The one I have is an 88 manual using the headlight control module.


Any pictures of where these three relays and the fog light relay should be located? And the fusible links?

 

I've got an 86 headlight harness around here somewhere, but no bird diagrams that old, and I'm shooting from the hip aided only by memory... The headlight relays should be up front by the headlight motors, on the rad support or inner fenders close to the motors. Pretty sure the other relay is on the firewall.

Wiring diagram(s) from another thread -









Damn, Google FTW!

 

Hi Drew

Thanks for your reply. I did find those diagrams however there are other versions which show the isolation relay in the same place instead of the LH actuator. There are even others listing fog light relay...

Anyway yesterday I tried to do some 'investigation' on my loom by calculating where the original wire lengths were ending.

Fog lamp relay is near the brake Booster on the LH wing. LH actuator is on the front left wing. RH actuator and Isolation Relays are on the same bracket on the front RH wing.

My new issue is now that I am suspecting that the PO replaced the Isolation relay and used a normal SPDT relay which although it works, I read it might burn the headlight switch. I am suspecting this as the blue and blue white writes going to the motors are bridged and the white supply is connected directly to hot. Also the yellow and black wires are swapped.

I am now going to try to investigate using a DPDT relay and putting some diodes for protection but first I need to confirm that my Isolation relay is actually not an isolation relay.