odd radio problem
So i have an odd problem with my radio that just began happening. Not always, but frequently enough to be really annoying, when i apply the brakes, the radio turns itself to full volume and i'm unable to turn it down until the brakes are released. I'm thinking i need to pull the dash off and look for wires that are shorting or touching eachother and shouldn't be. Just wondered if anyone experienced anything similar and had any input before i blindly start hunting.
it doesn't quite make sense to me, there's no wiring coming out of the back of the stereo that controls volume, just power supply, speaker wires, etc. so if it is a short, why would it turn up the volume rather than say blow a fuse or something? if it's an internal problem in the radio, why would it be tied to the brakes?
a little background info, it's an aftermarket stereo, which i installed when i got the truck about 8 years ago(99 f250 sd), never had an issue with it. i'm assuming it's unrelated coincidence, but it started happening immedieately after i replaced the power steering pump. the pump quit completely after making the typical whining noise, both in the power steering and the brakes for quite some time (i wasn't aware at the time of the fluid flush fix described on many sites). Also, for probably 2 years, i've had issues with the interior lights and ignition switch not turning off, which seems a common problem caused by a faulty door switch, which i'm assuming is also unrelated.
Any advice or pointers as to what or where i should be looking for would be appreciated.