I have a 88 Trans Am TPI 5.0 engine and engine harness in a 87 Trans Am Body. The brown wire or the L PED does not have power when the key is in the on position so therefore my alternator does not charge. the brown wire goes from the alternator to the cluster gauge. I took the instrument panel off so it shows just the 2 connectors in the back and i checked for resistance from the wire up at the alternator to the instrument panel on C2 number 12 in the back of the dash where the instrument panel hooks up to and the resistance is 1.2 so if its that then there should at least be some voltage up front. i know all 3 of those wires up at the alternator is suppose to have power. What else can i do to fix this? Thank you!

 

I am going through a similar problem. I think it's been isolated to the ignition switch. It's not providing an output to the accessories (coolant fan, HVAC blower, power windows, etc), orange wire. If I read the wiring diagrams right, the sense wirw for the alternator comes from the same place the coolant fan gets its power.

 

have you got anything figured out then? or maybe a little further then i am? Brand new battery and alternator so i know its not those. Could i just give that brown wire voltage from a power source? or tap into that ignition switch and if so what color wire on the switch?

 

It was the ignition switch. Now the alternator charges the battery with the motor running. I got that fixed, now the ignition lock cylinder decided to break. Anyway, it's been loose fitting on the column for a few years, guess I've been lucky until today. Now I need to pull the wheel to replace the cylinder.

 

how hard what it to put a new ignition switch in? What were the steps to take it out?

 

I didn't do it, but it does involve lowering the steering column (unless you have small hands and are double jointed). I was quoted about $15 for the switch and less than an hour to put it in. I would have done it, but I have no space in the garage and it's raining like crazy here in Western WA. In this case I'll gladly pay for someone else to do this.