Front door speakers issue - 3rd Gen

[mcaz5]

So I'm getting ready to head to school this morning and my buddy hops in my 4runner and immediately says it sounds like there isn't any sound coming from my front door speakers. So I check the fade and balance and everything's set to 0. Then I set the fade to only the front and sure enough muffled speakers, but that's not the problem. When I set the balance to the left or right speaker they sound like they work perfectly but as soon as I set the balance back to 0 they sound muffled.

I have a Pioneer 4300 UB and factory door speakers with subs in the back.

Any ideas guys? Thanks!

 

[mcaz5]

Okay I was playing around with this a little more. When the fade is set to front and the balance to 0 the song sounds exactly like an instrumental song. When the balance is set all the way to the left or right speaker, both speakers play and work exactly as they should. So right now I've just got the balance set all the way to 1 side. And everything works fine. Do you think when I installed the head unit I could have cross wired the balance wire some how?

 

[riceandpho]

Check the harness and speakers if u change them out, sounds like a reverse polarity wire on a speaker.