I am needing help swapping from 84 tail lights to formula tail lights. I have decided to go the route of cutting and splicing pigtails and I think that may not be possible without doing the whole harness. I have done the parking lights and turn signal so far and signals work with the switch however they also come on the the brake is pressed. Has anyone done this swap before by splicing? I also have a complete harness should I have to do it that route but I’d much rather cut and splice. There has to be some wire that just needs cut to remove the brake switch override. I’ve used this forum post (https://www.thirdgen.org/forums/electronics/626589-firebird-tail-light-swap.html) loosely as it goes the other route for the swap. I also do have another harness it says 91.5-92 that is complete. I also have the car that I took the lights out of’s harness but it has been cut at the rubber boot where it starts to go behind the tail lights but I could splice that back together if required.

Any help is much appreciated. Thank you.

First pic the original lights

Second pic the new lights

 

It's not common to swap from TA taillights to 85-92 base Firebird taillights, but I'm sure it's been done, so maybe one will post up. Usually the swap is from base bird tails to 85-90 TA tails. And that thread shows a simple way to configure a harness to make 85-92 base Firebirds work with 85-90 TA taillights, though not factory-correctly.

An opposite conversion, like you're trying to do, isn't as simple, because 82-84 and 85-90 TAs' blue brake wire is looped to the yellow and green turn signal wires at the connector beneath the steering column. Examine yours to see what I mean. That's why your signals are illuminating when you apply the brakes. 85-92 base Firebirds, even 91-92 TAs, aren't wired like that. Their brake and turn signal wires are separate all the way to the taillights, which is what you'll need to accomplish.

You said you have a complete 91-92 harness, but complete from where? From the steering column, back? Because that's what you'd need. If it's simply from the connector at the rear of the car, back, then that's not enough. Plus, that 91-92 rear connector won't plug-n-play with the rear connector on previous years, like yours.

If the interior is out of the car, then a complete harness swap, steering column to taillights, will be easy. Otherwise, you'll have to pull up the driver's side edge of the carpet, and all of the driver's side trim panels, because that's where the harness runs along the interior of the car, which you'll still have to do if you run a brake wire to the back.

 

https://www.thirdgen.org/forums/auto...ml#post6124395

 

Sorry, AJ, I hadn't looked at the link you provided. You stated that you were cutting and splicing pigtails, so I figured your link was to the thread that NoE provided, and that thread is not the one to follow for your swap. It's for putting TA lights into a base Firebird, and it is as simple as cutting and splicing pigtails. In fact, I did something similar. But you're putting base Firebird lights into an early Firebird/TA, which is different, and the thread you linked does address that, though it seems overcomplicated. So how "loosely" did you follow it?

You would've had to add four 194 pigtails for tail-only sockets, by connecting them to the brown tail wire and the black ground wire. And you would've had to add the brown tail wire to four 3-wire pigtails, where the other two wires are the black ground wire and a separate new brake wire, to create brake/tail sockets. That leaves the two turn signal sockets, which should be 2-wire sockets, where one wire on each is the black ground wire, and the other wire is the yellow signal wire (on one), and the green signal wire (on the other). But you've still got brake current running through your signal wires, so your goal is still to get the brake current separated from the yellow and green turn signal currents.

I'd said they were combined under the column, but I have, what I believe to be, such a connector that I cut out of a TA harness, and it looks more like a rear connector. But It's been so many years ago that I don't remember which it is. It has a white wire looped onto two terminals, which probably applies brake current to turn current, alternately, but that's just a guess, because my base Firebird isn't wired like that.

In his picture, he's cut the blue wire off of the car's side and extended separately, but I'm not sure that was necessary, nor was cutting the white wire at the brake switch under the dash. If I'm right, which, again, is just a guess, then eliminating that looping white wire might free the turn signal currents from the brake current. Then you could test each terminal to see if one is sending out brake current (if one is) and run a wire from that terminal, as a new brake wire to the brake/tail sockets. Of course, if your car's connector doesn't have such a white wire, then nevermind lol. But you've still got to isolate where the brake current is being combined with the signal currents and separate them.

 

Okay then, would 91-92 GTA style tail lamps be a direct replacement for an 82-84 TransAm?

 

I have put the Trans Am taillights into base and formula firebirds, no problem. I also wire them so all the lights have the high/low filaments in them. Not sure on the 1990 and later stuff, looks the same but I have not personally done those.