Audio Systems: grand prix, amp output, rear speakers

Question
QUESTION: Have 02 gp with factory sound,cd,6 speakers,equalizer, lost back speakers last yr. Occasionly back left will work,after I have checked and replaced fuse for amp, and radio. Should clarify, fuses are not blown, but after replacing speaker works for awhile. One source said it was amplifier. When it was working sound was excellent. Just want to get more info before replacing. thanks
ANSWER: You must check the wiring between the head unit/amp output and the speakers.  Was the speaker that you replaced defective?  If so, you may simply have overpowered the speakers and burned out the voice coil.  They will often come off and on when coils inside the speakers are burned from over powering.

If it was NOT defective when you replaced it you must assume it to be either the wiring between the head amp and the speakers.  Corrosion and shorts are not uncommon.

ALSO: There is a possibility the head amp is defective. To check for that you can check it several ways.  If you can get to the back of the unit and reverse the connections between the fronts and rear speakers, then the back ones would now work reliably and the front ones would not.

Or, if you can get a third speaker and connect it directly to the outputs, one at a time, to the back left, then the back right you can find out if the amp works okey.

So, you must do some testing/checking to verify what is going on.   

Conclusion:  You must determine if overpowering (turning up the volume too high) is damaging the back speakers. OR, if there is trouble in the speaker wires going from the dashboard unit to the speakers.  OR, if the amplifier feeding the rear speakers is defective.

Let me know if you need more help or have further questions.

c


---------- FOLLOW-UP ----------

QUESTION: thanks alot for reply. I didn't explain well. Should have put comma after replacing. I meant to put fuse back in place. Everything is original, no speakers have been changed. these cars have been known to have some electrical quirks. but twice after checking the fuses, the one speaker in back works for awhile. brother has grand am and dealer put in new fuse block at 1 yr old. thanks again

Answer
My reply remains the same.  The conclusions remain valid.  If you are certain the speakers are okey, then concentrate on the head/dash unit and the wiring.

If the fuse block needs changing it is because of faulty wiring.

Yes, all GM cars are quirky and that is why I am suggesting you check out the wiring carefully.  The electronics is made by the old Delco people and they are quite reliable.  But the wiring and harnesses and fuse blocks are made by GM.  That is the problem in many cases.

In some gm cars the owners have had to just ignore the wiring harnesses and run new, separate wires to the back speakers.  Or, add an external amp and wiring to replace completely the existing stuff.

Some of the newer cars multiplex the wiring and have data information crawling on the speaker wires that cause interference problems, but I don't think this is a problem with yours because of its age.

Now, finally, if you say checking the fuse causes the speaker to work for a while, it is possible there is an intermittent condition around the fuse block. If this is so, you can go around it with your own wiring; tricky to do, but you can cut the wire feeding both sides of the block, connection a pigtail fuse from one wire to the other completing a bypass operation.  

Hope this clarifies.  Let me know if you need further.

C