Audio Systems: Rear Car speakers only work when car is hot., electronics problems, rear speakers

Question
My rear speakers work only when the car is hot.  For example if it has sat out in the sun all day.  When it's cool in the evening or whatever, they do not work.  I have tried a different head unit and it exhibits the same problem.  I have not yet checked continuity from the head unit to the speakers since I don't have a diagram.

This is an all factory (pontiac) stereo and I am getting ready to upgrade my speakers all around, but don't want to waste money on the rears if I can't get them going.

Thanks for any ideas you might have - Howie  

Answer
Howie,

 this sounds like one of those weird electronics problems that sometime cant be explained, my best tip is the problem is in the speaker themselves, so go on with your replacement and that should fix the problem.. if not the only other place would be the wiring which to really isnt the logical place but  can easly be fixed by running new rear speaker wires to your headunit... if you are planning on upgrading your speakers without swaping your OEM head unit you will need a wiring diagram in the event replacing the speakers dont work .. best place to find this is by buying a haynes repair manaul from your local parts store.. but if 12 bucks doesnt fit what you want to spend on the diagrams you can give pontiac's customer service line a call tell them you need the color codes for your radio wiring explain make model ect.. and they should be able to help you unless the car has some age on it ... hope this helps you out if you need anything else let me know


thanks

CM