Small problem with deck, I think

Alright, I have a Pioneer 200 watt deck connected to the 6 factory speakers in my car.  I add a pair of 12" JBL subs and Lanzar Vibe 420 amp.  The amp is 800 watts, 4 channels.  For a while I just used 2 channels to power the subs and left the others unused.  The other day I tried to bridge the subs by connecting 2 channels to each one, and the subs stopped working.  They didn't blow out, they just didn't make any sound.  So, I set the wiring back to 1 channel per sub, and they work fine now.  The problem is that my other speakers don't.  The deck turns on and plays, but the only sound is from the subs.  Can somebody here tell me what the heck happened?

Check any speaker wiring near wherever you were working with the amp/subs as you may have accidently shorted out a speaker wire.  Not all that likley but it is a possibility, and you would definitely have the same symptoms you're having if this was in fact the problem.

Just to make sure, you used the head unit's RCA outputs to go to the amps, right?  Or did you use a line-out converter or the amp's high-level inputs?

Moved the fader up & down, and the deck stayed put.  To get at it I need to take my dashboard apart so I generally leave it be unless I have a major change to make that I know specifically what I'm doing.  Which isn't very often, lol...