Once again I tried to search the older threads for answers but found nothing. When I bought this disco it had a sony head unit in it. I replaced it with an alpine and apac oem from crutchfield. I have engine and headlight noise in the radio, I replaced alternator put new wires and plugs in even grounded the radio which took some of the engine noise out but not the noise from the headlights . I've talked with the crutchfield tech rep he didn't really have any answers. Any help on this would really be appreciated.

 

Check your antenna, a loose plug can allow interference.

 

Well, it could be a number of things: Plug wires, improper radio ground, Motor/alt not properly grounded, bad alternator capacitor, etc. You can change the alternator capacitor really easy on that alternator. It's only a couple bucks and right on the back of the alternator (probably need to remove the alt and it's under the black cover). Get a new one from an alternator shop.

Now, back to your original radio, my 98 radio wasn't working either. I could hear faint audio through the speakers, but nothing else. Problem turned out to be a yellow relay behind and above the glove box door. If you take your glove box door out, it's the relay furthest to the L (closest to the tranny tunnel). You might try sticking the old one back in there. Also, there's a fuse on the radio amplifier downbehind the passengers kick panel (black aluminum box mounted vertically to the metal body behind the kick panel). You can remove it w/o removing the amp. Just thought I'd throw that bit of info out.

 

I never messed with the relay, I checked and they are all plugged in, nothing loose.I don't know if it makes a difference that the amp is under the drivers seat. (Just went out and checked behind the kick panel just relays behind it) I will check the motor/alt ground thats the only thing that I haven't checked yet, since it is a new alternator that was installed that could be the problem.

 

I know when using my FM Transmitter for my iPod, plugged into my ciggarette lighter, I recieve nominal alternator noise.

Make sure the connecters to the new head unit are properly shielded.