Hey guys, had a customer come in the other day with a 85 trans am and the headlights wouldnt flip up. The isolation relay was filled with rust. I then found out this relay is discontinued by gm and no parts stores has them. I figured out how to make this work with 2 5-pin relays and a diode. For anyone stuck with this problem PM me and i will make you a relay. Local part stores carry the actuator relays, i had to replace them also.
Mark

 

I just used a regular SPDT auto relay, works fine.

 

Sorry. may I ask what a SPDT relay is?

 

Single Pole, Double Throw. Means the output pole is connected to the 'normally closed' output terminal when the relay is not energised, and flips connection to the 'normally open' output terminal when it is energised.

 

If you used a spdt relay did you tie both headlight motors together as in the circuit layout the isolation relay is dpdt isolating the headlight motors?Thanks

 

I did this several years ago, can't remember. Just looking at the factory circuit I must have, along with adding a diode to prevent the 'off' signal from the switch backfeeding and latching the lights on. It's worked without fault since - I will go look at it what I did when I get a chance.

When I bought the car, the original iso relay was dead and the PO had used a regular relay, badly wired + installed, and not working reliably. While doing an electrical overhaul, I found the correct replacement relay was either unavailable or some exhorbitant price, so decided to formalise the standard relay arrangement.

 

Hey TreeFiddy,
Any chance you have the wiring diagram for changing from the stock actuator relays to the SPDT 5 pin auto relays?
I've got plenty of them but just wanted to know how to wire them up properly the first go instead of trial and error.
I know there's one plug with 3 wires and the other with 2 but not a clue how to wire to the 87,87a,30,80,85 points

 

Hey Stuie, sorry been on a bender down the south coast the last couple of days, just logged in

Are you talking about the isolator relay referred to above, or the l/r actuator relays? The iso relay can be replaced with the standard SPDT 5 pin auto relay, but the actuator relays are DPDT. You would need to use two standard SPDT's to replace one. I've never done this but don't see why it wouldn't work.

Lemme know which one you want, iso or actuator, and I'll rough you a diagram or pinout.

 

Hahaha, must have been 10-15 minutes too late.
Both now. Tried to use the SPDT relay in place of actuator and fried the isolation relay.
If you can give me a rough diagram of each I can hopefully rig the SPDT relays or buy some DPDT ones.
Thanks

 

Ok mate! Just popping up the pub for lunch, I'll whip something up in a few hours time. I don't think I've ever seen a DPDT version of the standard relay, it'd need 8 pins which I've never seen, so a couple of regular SPDT's is probably the go. I'll give it some thought once my head clears

Just noticed you started a new thread on this topic, might move the discussion there.

 

My wife had her isolation relay burn out on her 1986 Firebird. After months of research I put two years of electronics school to work and built a replacement. Watch it in action on YouTube.


Working up the plans now and will post them in another thread soon.