Audio Systems: SPEAKER PROBLEM, external amplifier, blown speakers

Question
hELLO

My son's Pioneer aftermarket CD player quit working completely. We took the car to a car audio place and they told him that some fuse behind the unit has blown and cooked the unit and his front speakers ( which are only 2 weeks old)  My son put a used unit in that he got from my other son who just took it out of his car (it was working just fine).  The head unit does work but there is only intermittant sound.  Most of the time there is no sound, but when there is the front speakers that he said were blown and playing.  What could be the problem?  Did the guy possibly do something when he checked this fuse?  If the front speakers are blown does this mean that the back speakers will not function? We could not speak to the installer that originally worked on the car and they were booked and could not look at it but a guy said that it sounds like to amp built in the head unit knows the speakers are blown and is not sending music as a protection device.  Is this true? What can we do to get sound until the supposedly blown speakers can be replaced.

Thank you

Answer
You must learn the basics of the installation.

If the head unit has built in amplifiers, then the output wires do directly to the speakers.  You must check everything carefully.  If wires are crossed or shorted it will cause the problems you reported.  When a tech says the speakers are blown it does not mean the actual speakers but the speaker channel and it is usually the amplifier or the wiring that is wrong.

If the head unit has rca outs that feed into a separate amp the analysis is the same, except the external amplifier is the driver to the speakers.

Here is what I recommend you do - since you know how to remove an reinstall the head unit.

ONE:  Bench test the cd player. Do this by pulling it out and powering it up by running some wires directly from the battery.  Then, connect just one stand alone speaker to one channel and check it out; then one by one check all the channels. This will verify the unit is working - or not.

TWO:  Before reinstalling, check each power line for the proper voltage and each speaker line to make sure they all go to the speaker you expect AND check for shorts to ground or to other speakers. You may have to buy a VOM to do the checking. If so, the one I recommend is at the electrical department at Walmart for $9.83.  The one in the automotive department is more expensive and not as good for auto work.  It is very simple to use and can measure the 12v lines and do continuity checks (when in ohhmeter setting) on the speaker lines.

THREE: Then, and only then, when you have everything checked and verified to your satisfaction can you reinstall and test the system in the car.

Good Luck,
Cleggsan