I have a set of Polk speakers wired behind the seats and I installed an aftermarket head unit (Kenwood BT555U). I connect the + and - wire to the rear speaker inputs in the rear of the HU and I'm not getting any sound. I'm not a TOTAL noob, but am I overlooking something simple as to why there wouldn't be any sound? No external amp, just speakers wired to the back of the HU. Thanks in advance and sorry for the simple question!

 

The one simple cause would be if the headunit's fader control was set
all the way forward.
If that's not it, there are a few things that aren't completely clear from your post:
- did the rear speakers work before you installed the new headunit?
- are the rear speakers wired directly to the headunit's harness, or
did you connect the headunit's rear speaker wires to the corresponding
wires in the adapter harness?

 

Probably just hooked it up to the wrong wires. Headunit wiring is very basic, im sure you just missed one. The speaker output wires from the HU are usually as follows: grey/grey black stripe. purple/purple black stripe. green/green black stripe. white/white black stripe.

 

In case anyone was wondering, I figured out the issue.

For whatever reason, the Kenwood HU I have only plays BT streaming audio through the Front speakers. I switched over to another source (USB) and now it plays through all 4. I find that pretty odd that a receiver can't play BT audio through all 4 speakers. Oh well.

PROBLEM SOLVED!

 

Whattttttt. That is a bit odd. I use BT streaming daily, but I dont use a rear channel so i wouldnt know... At least you figured it out!