Car Stereos: radio problem, internal amplifier, best case scenario

Question
ok so i bought door speakers and 2 ten in subs i originally hooked the new door speakers up to the deck i bought but the speakers keep cuting out when i turned u the vol so i figured they need an amp so i ran a wire from the door speaker to the amp and i just got bass and not voice thur it so i hooked both the wires from the amp to the speakers and the speaker wire that was hooked up to the factory speaker and it work for a sec then nothing at all my deck still powers on and everything works on it but i cant get any sound to come thu the speakers i looked at the cars fuse and the one in back of the deck both were good and the amp has power to it but wont power up now. any suggestions? could my deck be bad even tho it powers up?

Answer
Hi Marcus,

There's a chance you've fried something.  What you needed to do to get full sound out of the speakers was to hook them up only to the amplifier, and disable the low pass filter on the amp (probably a switch).  You'll need to test everything one by one.

First step is to disconnect everything.  The only thing connected should be +12V +12V switched, and ground to the deck.  Then, get another speaker you're positive works, and test it on the 4 sets of speaker leads coming out of the deck.

If that works, the deck is fine, and you can move on.  If not, you may have fried the deck's internal amplifier.  Step one is to check the tiny fuse that is usually in the back of aftermarket decks.

Then move on to the amp.  Wire it up, and then test its outputs one by one with a known working speaker.

Once you're done that, test your speakers with a source you know works.  (Don't use your home stereo, as it's usually rated for 8ohm, and car speakers are 4ohm, and a best case scenario is that the home stereo detects it and cuts out.)

Another quick way to test your speakers is to use a multimeter.  They should provide 4 ohms across the circuit.

Good luck,
Justin