I have a Pioneer DEH-P3500 that was installed a couple of months ago
with basic RCA cables plugged into the AUX port of my head unit. I
have a Y-adapter that converts the RCA into a 1/4" headphone jack so
that I can plug in an iPod, laptop, etc.

Unfortunately, I get no output from the unit. The auxillary device is
plugged in correctly, and is at full volume, so there isn't a problem
on that end. I've tried for days and would like to get this working
without taking it back to the shop that installed it, but I'm thinking
that I will have to.

Any ideas from you helpful people would be appreciated.

Thanks,
Ryan