Alpine CDE-9870 and my 1992 GMC Sierra and Beyond?

Question

My old head unit bit the dust. I tested all of my speakers (only front ones were factory stock) the old fashioned way: a D-cell and 9v battery. All gave contact static except for right front. I bought a set of Pioneer 4"x6" for the front, installed, and retested. Every speaker now works.

I bought the Alpine CDE-9870 head unit (my first Alpine) and a new wiring harness. I wired the harness and Alpine plug together (except for rear speaker plug, which is no longer in use). I plugged the Alpine in and it turns on. However, there is no sound from any of the speakers (except for small pop when turning the head unit on).

I tried the POWER IC setting (both on and off) with no help. I hooked my Bose into the external RCA connections. Both of those produce sound, but nothing to the car speakers.

I tested the speaker lines with my original speaker, with no results. I also tested with a flashlight bulb. Nothing works.

Bad head unit or bad wiring?

Thanks in advance,
Doc

I thought about what you said and disconnected all speakers. I used the radio wiring to test each speaker and found one that was grounding to the body instead of grounding back to the radio. I fixed it and I'm playing with power now. Thanks for the help.

Answer 1

Most likely bad wiring. It sounds like a shorted speaker wire. It's possible one of the terminal connections at the speaker has come loose and is touching the other terminal, or dash metal. This will shut down the head unit's internal amplifier. A speaker wire that is pinched against dash metal will do the same thing, if it's trapped under the edge of the speaker or has a mounting screw run through it.