Most commonly this happens when some of the speakers are run by a remote amplifier. You either need to bypass that amp or you need to make it turn on. On older vehicles the amp simply got a turn-on signal from the radio. That would be the yellow or blue, (typically), wire on your new radio labeled "power antenna", "amp", or "switched power". The mating wire would be in the original plug.
On many newer vehicles, the engineers complicated the circuit unnecessarily. Instead of a wire for the turn-on signal, it is a digital signal sent along the data buss. There are some aftermarket radios that will generate that signal, but you are better off just bypassing the amp.
Connecting front and rear speakers together is not a good idea if you do not know how many speakers each channel can handle. Most original radios can run two speakers on each channel, but with aftermarket radios, the additional load could stress the output ICs. That type of failure can be identified and is rarely covered under warranty.
Feb 22, 2017 at 4:37 PM
