Electrical gremlins are driving me mad!

[VetticusSupersonicus]

Sorry for the bother, but this is driving me up the wall. I bought an Alpine CDM-7874 from a local A&B Sound shop earlier this month. I got it home to see what I had bought and all the wires from the harness had been snipped and such, indicating that someone had gotten it half-installed and brought it back. I went in and asked for a new unit and this little poopie gave me this bullpoopie story about how they didn't have any more in stock and how it'd take weeks to get another. (What happens if someone buys one?!) "If something's wrong with it, bring it back here and we can order a new one." Fine. So I pull apart my interior and wire it all up, which was tougher than it should've been because my entire electrical system is a hack job. So I have it all installed, turn on the power, and the front left speaker is garbage. All I can hear is static and a bit of the actual music. Something must be wrong with the speaker, I thought. That must've been why the last guy didn't bother hooking up these ones in the dash. There was some bad wiring with butt connectors and non-audio wire, though, so I figured I might as well replace that and see if it helps. Nope. So, I unplug it and resolve to replace it later. I turn on the power and all of a sudden my right dash speaker is doing the same thing! It used to be crystal clear! :mad :mad: mad What could possibly cause this? Is it a faulty head unit? I dearly hope it isn't, because I don't want to do this all over again. I just can't think of any other explanation, though. I've made sure that the audio wires run along the top of the dash on their own, instead of bunched together with the ignition wires and such, so that couldn't be causing the disturbance. Other than that, though, I'm lost. Anybody have any ideas before I set the whole thing ablaze? :cheers:

[_Nomad_]

I am assuming this HU is in your ’76 Vette? In that case, you may as well do what my friend and I did to his ’76, and that is…redo everything! :crazy: :lol:

Ground your HU with 10-gauge (yep, 10-gauge) straight to the battery, I know, the battery is in the rear on those sharks and it will be more work, bummer, but grounding is a problem on those body styles. Also run your power straight from the battery same as the ground. Run all new speaker wire too. Basically you don’t want to be using any of the old wires that are already there, especially with the description you gave of those old speaker wires. Your goal is to effectively bypass all old wiring harnesses or DYI wire jobs other people have done over the years. After hooking up decent speakers in correct polarity you should have the sound you were expecting. If not, then the HU may be a concern. At least you now have a clean slate to diagnose from. This description does not including any amps you may want to install. Do this first before installing amps to make sure the HU is properly powered, grounded, and sending correct voltage and signal. If everything is fine, then install your amps.

Also, always be wary of an audio shop blatantly selling a returned HU like that without telling you what it is and charging full price for it. The fact they have no HU’s in stock (Lack of inventory) says something about them too. Unless it’s some closeout sale item you bought, that’s different. Then it’s basically buyer beware.

Good luck and keep us updated. :seeya

[92TripleBlack]

I remember problems with the old C3s. I did a bunch. For the most part, the safest thing to do is run new wires. I wouldn't be suprised if you had the speakers run with a common ground. This is where the ground of the car is the speaker negative. Older cars often wired up this way. This would fry a modern deck. Power up the deck first without any speakers and test the speakers one at a time with a test speaker to make sure the deck isnt' the culprit then make sure the speakers you have don't have the negative wires connected. Dodge was the last maker to get rid of this practice which they did well into the mid 80s.