2002 Mustang GT coupe
I'm planning on upgrading to an after market head and I'm a little confused from watching youtube videos. My 2002 Mustang GT coupe stock radio has 3 multi-conductor OEM harnesses plus the antenna lead plugged into it. But all of the videos I've seen only connect the aftermarket radio to just 2 of the OEM harnesses. So what is the third OEM harness for? I'm assuming that it has something to do with the fact that mine has a premium sound system? One of the youtube videos I've seen show 3 harnesses being disconnected from the stock radio but all the others have only 2 harnesses being disconnected. What's the difference and does it matter that the aftermarket system doesn't use the one OEM harness? To complicate things, some Metra harness interface kits have just 2 harnesses while some Metra kits have 3 and both kits are shown to be compatible with my car (according to Amazon). And then there are videos saying the third harness in the kit isn't used.