I recently replaced my non-working factory radio with a Kenwood HU and also put in some new speakers. While swapping this stuff, I ran into some interesting phenomena about the GM way of doing things.

First the speakers. It's no shock that the factory uses a funky connector that won't begin to hook to normal speaker blade terminals. Not much of a problem because BB sells an adapter that plugs into the factory harness and gives you two little pigtail wires with blade connectors on them, one narrow and one wide. The problem comes in where the factory wires the front connectors opposite from the rears. This means that if you use the BB adapters front and back, your speakers will be out of phase. Nice huh? Crutchfield supplies two different adapters if you buy all your speakers thru them. The front is opposite polarity of the back.

The second funky thing is power. The factory uses a switched red wire that is powered thru the RADIO fuse. It's a whopping 10A. The orange, always hot wire is powered thru the ARC fuse and it's 20A. Apparently the factory radio used the always hot wire to actually power the radio amplifiers and internals. The switched red wire only supplies a miniscule amount of power to the factory radio. Aftermarket radios use the orange wire to power the memory of the radio and nothing else, all other power comes in the switched lead which is only capable of a max of 10A.

Even though it's unswitched, the orange wire would be a better choice to power the radio. A relay could be used to make it all work just like stock and turn the radio off when the key is turned off.

 

Great info. Thanks.

I don't understand why GM would mess with the wiring (i.e.,polarity) between the front and rear speakers???

 

I guess so that people would be inclined to take it to the dealer for upgrading after they didn't like the sound of a replacement. I have a service manual and they are very careful to make sure they don't indicate polarity anywhere in the schematics. They use A and B and even that is reversed front to back. They give you enough info to hook it up right, but still not know what polarity anything is.