Stock, the base 91/92s Firebirds use 2 separate wires to send signal for the brake & turn lights, same as all the Camaros did. The under dash mod is needed to combine the different signal (bake & turn) into 1 signal.
BigBadLou did it for FYRCHKN for base lights, when FYRCHKN put older tail lights on to run one of my STS controllers.
If you took the wiring for the rear too, that would make the conversion MUCH easier to do. The rear would be done & just hafta connect them un der the rear seat. The 89 set I took out, had a simple plug connection there.
You'll basicaly be doing the opposite of this conversion. I'll paste the part of my STS instructions, that applies to it.
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Base TA, ‘91/’92 TA or ’82-92 Camaro installation
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This conversion procedure consists of two main steps. They BOTH need to be performed at the SAME TIME! The vehicle would be illegal and unsafe to operate unless both steps are finished!
STEP 1 - steering column wiring
Remove the plastic driver side under-dash cover to access the steering column wiring. It might help to also remove the vinyl wrapped knee panel to gain better access to the harness.
Locate the white wire that is the last wire in the connector.
Find the brake switch. It is mounted on the pedal bracket, just rear of the brake pedal. The brake pedal lever is actually resting on it.
The switch has three wires.
On Firebird years 1989 and older, the wire colors are:
- orange
- light blue
- light blue with a black stipe
On Firebird years 1990 and newer, the wire colors are:
- orange
- light blue
- yellow
We need the light blue wire. Cut it as far away from the switch as possible. Then if you can, connect it directly to the white wire which we located earlier. If you can't, you will need a piece of extra wire to connect these two.
That's in, that't the whole fix under the dash.
In case your steering column connector from the turn signal switch does not have a white wire, you will need to install a GTA turn signal switch which can be purchased at any parts store for $25.
STEP 2 - tail wiring
From the inside of the trunk, remove the plastic trim piece covering the rear panel. Then remove the plastic wingnuts that hold the DRIVER SIDE tail light to the rear panel. (no need to remove the passenger side tail light).
Remove the corrugated plastic wiring loom to expose the wires. Find the light blue splice.
In the light blue splice, locate the wire that goes into the wall (left) and another wire that goes to the passenger side tail light (right). Cut both of these wires.
Cut the yellow wire off the lightbulb socket and connect it to the light blue splice.
Cut the dark green wire in the harness (make sure you have enough length) and connect its left part to the light blue wire going to the right (passenger side) tail light.
You are DONE!
Of course TEST THE BRAKES AND TURN SIGNALS. The turn signals will now flash the red lights. If the brake lights are on and you turn on a turn signal, that brake light will start flashing (with the other brake light still on).
