accessory wire for gm

I have had two different newer model gm vehicles in our bay in the last week. one for satelite radio and the other for GPS. both i had troubles finding a large enough accessory to tap into. the only way i could think of was to use a relay. so two things does anybody have a different solution also just wondering about doing a remote start in one.

what type of gm vehicle was it? there are a couple that you need to relay off the battery withe the accy wires (18/20 awg wires ) Tire Proz Stillwater Mn

High End Restyling and Comlete Repair

one was a 05 grand prix and the other was an uplander i forgot the year

On some of the older cars, the RAP (Retained Accessory Power) relay could be found in the fuse box. If you tap a wire into pin 30 of the relay, it'll even hold power until you open the door, just like the factory accessories.

careful of the uplander, if you grab the brown acc wire from the ignition switch it can cause the van not to crank. Shaughn Murley

Install Manager, Dealer Services

Visions Electronics

Red Deer, Alberta

The problem is you need to determine whether or not you are applying power to the wires (remote starter) or drawing power off the wire (adding accessory like satellite radio). Some newer GM vehicles can have a relay added onto the accessory wire in the ignition harness and some can't. It depends on the vehicle, year make and model. The ones that can't handle a relay are the ones where the ignition switch only switches a very low current onto the various wires (Igntion, starter, accessory). The BCM feeds this low current through a wire to the igntion switch and the igntion switch then sends back power on the other wires to the BCM depending on what position the key is in. Connecting to any of these reference wires can cause serious problems with the BCM. The car may not run or start or have other weird electrical problems. You need to determine where the car manufactrurer wants you to hook accessories up to. The dealer can help most times if you ask nicely. Many GM vehicles actually have a plug in the dash someplace which provides these wires to add acc's. If all else fails, try using a source at a fuse box to trigger a relay. The relay can get its power from a wire you run out to the battery and fuse it. In the case of the Uplander there is a thick yellow wire in the passenger's kick panel that provides a RAP source of accessory power. You will also find a thick battery wire there.sparky