2004 impala auxiliary input problems

If someone has already asked a similar question, I apologize, I looked and did not see anyone else who had a situation similar to mine.
A while back I had a car audio "specialist" install a pac auxbox with a 7pin din based 3.5 mm input in my 2004 Chevy Impala. The car is the base model, the stereo has a CD player and a tape player, but the car is not equipped with onstar. Soon after I had this installed the battery began draining rapidly, the problem was bad enough that the car could drain to completely dead within 36 hours. I pulled the fuse for the radio, and recently had the time to go back to the original installer. I asked him to go in and wire the auxbox to something that didn't constantly draw power. He wired it to windshield wipers. While it works alright most of the time, on any drive over a half an hour it seems like the device is overheating or something b/c after a while one of the speakers will go out for a little while. When I start the car back up again the problem is fixed. And then there's the issue of rain, whenever I turn on the windshield wipers there is a massive burst of feedback that can only be stopped by disconnecting and the reconnecting my mp3 player. I need something I can wire the auxbox to that is either controlled through r.a.p. or failing that I need some switched accessory source of power that I can wire it too. I don't know much about car electronics, so any help would be greatly appreciated.
Thanks

what kind of jackass did you take your vehicle to? he should have found a r.a.p. source or made one with relays, or at the VERY LEAST hooked it to your accessory wire at the ignition switch. i personally like to relay off of the remote turn on wire from the factory deck.

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A DMM is a beautiful thing.

MECP Advanced Installer Certified.

I was asking myself much the same question, but I think the issue is that the r.a.p. sources are controlled via a command sent through the GM databus. I'm assuming that the idiot I took it too used the wrong wiring harness or something. My mechanic looked at the way this guy set it up, and while he's not a car audio guy, he said that none of the wires in the wiring harness were switched (i.e. they were all constant). Are there any specific wires off of the factory radio that should work, and (keeping in mind I know very little about wiring this) where would I be able to find a source of accessory power.
Thanks

if you really don't know much i'd say get your power from the orange accessory wire at your ignition harness. the wires coming off of your key cylinder.

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A DMM is a beautiful thing.

MECP Advanced Installer Certified.