Deck has power but no output to speakers
 

Just recently installed a Kenwood (KDC-X659) deck in a 91 pontiac firefly which had it's stock stereo installed at first. Refer to my recent post here: http://forums.beyond.ca/showthread....804#post4102804

I took the advice of sr20s14zenki:

"Best way i can recommend is to take a test light, and find your constant power, ignition power, and ground. After you have found those, take a 9v battery and start trying pairs of wire. Should hear pops thru the speaker you are energizing."

I matched all the correct wires and got power to the deck. I then connected all the speaker wires by testing each wire individually and IT WORKED! All the speakers were playing music perfectly and everything was looking up. But then something weird happened. When I drove the car home all the sound from the speakers stopped halfway through a song. I thought it was just a fluke and went home. The next morning it was working again. And now all sound has completely stopped.

I investigated the issue and found this:

The power is working (no blown fuse), all the speakers are working, I cut the crimped wires and tested with a battery (heard the popping noise) then reconnected the wires. -still no sound- I've went through all the settings on the deck to see if the speakers have been muted some how but still no luck. Has anyone experienced something like this before? Could this be from hardwire installation that the positive and negative wires from the kenwood deck plug in are connected to the wrong ones on the car wires?

Could be a bad ground, don't use the car harness ground wire, connect your ground wire from the headunit harness directly to the firewall (scrape the paint away)
Use this for a reference:

12 volts: White
Accessory: White/black
left front speaker: Orange +
Orange/black -
right front speaker: Red +
Red/black -
left rear speaker: Green/white +
Green/black-
right rear speaker: Grey/white +
Grey/black -

Just to clarify before I do anything, if it's a bad ground would there still be power going to the deck? There is constant power going to the deck with no issues. Just the speakers don't work.

Also, looking at the back of the deck there are two "cords". One black thicker chord on the left that connects to an adapter from the car. (is this a ground wire?) and a chord on the right that consists of all the speaker wires, power wires and a ground wire. (is this the ground wire that should be connected directly to the firewall or is the the left black chord?)

Your power, ground , and speaker wires will all be on one harness, which you can unplug from the deck. The black wire on that plug is your ground, connect it to the firewall, either way you have to remember that your factory ground wire in the vehicle is 22 years old ( Don't use it ). Go back and test your speakers as you did, when you initially wired up your deck, Use the chart I posted above for guidance and see if they "pop" still. If they do then it is not a speaker problem.The problem is related to the deck. You could even grab a 4 ohm speaker and hook it up seperately to each lead and see if there is output, make sure none of the other speaker lead outputs touch one another when testing.

Just to add, the black thick chord may be your antenna for the radio.