If it's the factory GM radio it's going to have a "theftlock" code system. Any disturbance of the power to the radio can lock it out.

Aftermarket radios need power on both wires to work. The yellow wire live all the time and the red wire live with the key on.

 

Moral of the story: Next time use the relay and wire directly to the battery.

 

there is power to both

 

Check that the radio is grounded. Check the fuses in the wires or on the back of the radio. Then try disconnecting the battery to reset it.

Also most aftermarket radios will not play if there is a short in any of the speaker wires. Some just cut the speakers off but others power down completely.

You could pull the radio out and test it on the bench. Use a good car battery or a power supply, apply +12 volts to the yellow and red wires and minus to the ground wire. Leave all the other wires disconnected. If the radio still doesn't light up, it's defective.

 

rookie of the year at what?
wire the fogs from the battery. Use a relay and a ground to trigger the relay
to send 12 volts to your fogs.
If you have constant 12 volts, and switched 12 volts at the head unit...... it's toast!
do this.. http://www.the12volt.com/relays/page1.asp

 

You know how there's both a constant 12V wire and a switched 12V wire going to the headunit? Check the constant 12V for power. For some reason on my old Civic I was installing an old stereo and all of a sudden it wouldn't work. I figured out my constant wire was dead, so since I was selling the car I just ran a new wire from the battery and put an inline fuse in it. I recommend actually fixing it though if it's the problem instead of taking shortcuts like I did.

 

On '90s Civics, (getting back to Civics for a change), the constant +12 comes from a fuse in the box under the hood. A lot of people don't know to check there. The "radio" fuse under the dash supplies only the power that turns on and off with the key (for the red wire).