I installed an MTX sub and amp in my 05 Impala last week. Being that its a PITA to install an aftermarket receiver in these cars, I kept the factory unit and wired the amp to the speaker level inputs. To do this, I teed the amp input wires from the rear speaker wires. With the speaker level inputs, a separate turn on lead is not needed for this amp, just speaker input is required to juice it up.

After the install, I turned the ignition on and the front speakers powered up. Interestingly, neither the rear speakers or the amp powered up. I started to investigate my wiring job (done in the dark and scrunched in the trunk in the fetal position) and unplugged the input lead from the amp. I plugged it back in and booya, amp and rear speakers powered right up! I chalked it up to a loose harness, adjusted everything, and called it a night.

The next day I got back in the car and damn, back to front speaker only operation. Went back to the same connector, unplugged it and plugged it back in, everything's working fine! I've tested this countless times, same result every time. As much fun it is to do the rear speaker shuffle every time I start the car, I could use a smarter solution.

My question is, how should I go about getting the amp and rear speakers to power up when I turn the key? I've got some ideas using switches and/or relays, but I would like to get some more details on how it should be done right.

This is what I would like to accomplish: rear speakers powering up at start-up with the ability to switch the amp on AND off at will. Any advice appreciated!!