My headlights would raise unless I rocked the switch back half way between on/off for the longest time, but just recently they quit on me all together. after some diagnoses found the issue was low output voltages from my isolation relay.
I couldn't for the life of me find a replacement relay online or a guide on building one, so here it is.

All of this applies specifically to a 1985 firebird VIN code F, but from what I understand, all thirdgen firebirds use the same relay. I dunno, check your manuals diagram.

First to verify the relay is the problem you'll need to check voltages at the relay with the wires connected.


#2 pin/yellow wire (raises headlights), #3 pin/white wire (lowers headlights), #4&5 pin/ blue/white & blue wires (motor controls), #5 pin/pink wire (motor controls), #1 pin/black wire (ground)
OFF: #2 yellow 0V
#3 white 12V
#4&5 bluewhite/blue 12V
#5 pink 0V
#1 black 0V
HEAD: #2 yellow 12V
#5 pink 12V
#1 black 0V
If these voltages check out then the relay is good and your problem is likely with the headlight relays or motors. If the yellow or white wires show low or no voltage, your problem is wiring. If the blue, blue/white or pink wire show low or no voltage the problem is in your relay.


If you look anywhere online for this relay you'll get directed to something like a Standard Motor Products RY130, this is the wrong relay and will not work.
So you gotta make your own,and will need:
2X 5 pin relays, I used Dorman 88069s since Oriellys had em in stock.
1X diode, I used a ACDelco 12135037 which fits in a mini fuse holder, also in stock at Oriellys.
-If the relays you get have a diode on the coil circuit then you don't need to add one.
10X female spade connectors
some blue and yellow butt connectors
Fuses/holders for the yellow and white wire if desired (both circuits are protected but I'm overly cautious)
And some 18 gauge wire.

Here is a diagram I made of this stand in relay.

Assemble your ugly mess of wires, connect it to your harness and your done.

Here is the finished test product, not pretty but it works.

cant upload a video so here's a gif of the test working.


Now just gotta splice it in and hide it.

 

You can purchase a replacement isolation relay from Rodneydickman HERE.
It’s his own creation since you can’t buy the exact GM one anymore. I bought one for my ‘84 TA. Was pretty straight forward to install.

 

Very nice work John, it's great to see someone else around here who knows electricity on a first name basis

 

I think I understand your design intent, which could be to use all common automotive components for ease of service. Whereas a single DPDT relay would suffice, the Bosch/Omron automotive style relays are typically SPDT at best, and even those are tougher to find than SPST whic seem to be used for about everything on a vehicle. I hope the diode is at least a 1N1004 or better, since two coils dumping through it simultaneously might take out a lesser component. People seem surprised that a 12V coil can peak over 250V when inductive energy is involved. I've never looked at the specs of the typical auto plug-in diodes but suspect that since they are found on AC compressor clutches and other heavier applications, they might be up to the task.

If you can weatherize your assembly, you should have a winner.

 

Well, since the topic arose again, and the internet is now more robust than it was 20 years ago, it was easier to find the specs today. It appears to spec almost exactly like a 1N1004, 1A, 400V, but without any surge or peak data - No shock there (see what I did with that?).

 

I bought the same one and mounted it to the factory location. Works great