Stereo + headlight interconnection??

[mishalah]

I recently installed a "new" factory head unit (with tape + MP3/IPOD plug) and CD slave unit. They all work great, but I had a strange "no sound" incident last week. I turned the unit on, everything lit up, all functions worked, but no sound came from the speakers. The owners manual says there is a fuse for an "amplifier" in the side-of-the-dash fuse box. It was ok, as all the others were. I could hear a slight "ping" sound from around the left side of the dash when I tuerned the head unit on and off. I thought maybe a relay had gone bad.

I resigned myself to driving all the way from NorCal back to Vegas without a stereo, then.....I pushed the "dome light" override button, and the speakers came on. Hmmmmmmm...ok. I wasn't going to complain or look any further as long as it worked. Next day it did it again. I tried the "dome light" button and it didn't help. Sooooo...being the deductive person I am I rolled the interior dash light adjustment wheel up and down a bit. VOILA! The speakers came on.

It has worked fine since (maybe one time no speakers that I touched the light adjustment wheel and the speakers worked but I may have had it turned down too much to hear). SO...what is the connection between the stereo speakers and the headlight/dome light/dash light adjustment switches???? Or, is this just some GM gremlin that no one knows what causes it?

[mishalah]

I'm still getting some kind of interaction between the radio on/vloume knob and the interior light controls. Most of the time it's the interior light dimming/on switch. When the radio won't come on I can rotate the switch up and down a little and the speakers will come on.

Nobody knows what is happening or why?

[777stickman]

With weird stuff like this it is most likely something somewhere is not grounded properly. Also state what year and model this vehicle is.

[mishalah]

Originally Posted by 777stickman

With weird stuff like this it is most likely something somewhere is not grounded properly. Also state what year and model this vehicle is.

'96 K1500 suburban. I just replaced the head unit and added the cd player. They both work beutifully, except for this strange interaction with the light controls. I did not have this problem with the original head unit, nor when trying another replacement unit that had a bad tape player (the original had the CD in the head unit). I am using the factory wiring harness and factory connection cable to the CD slave unit. No wires were disconnected or spliced other than unplugging and reconnecting at the unit(s).

One thing different about my "new" head unit is that it has a plug for an MP3 or IPOD. I haven't even used it, and even if there was a, inside circuitry problem I don't see how it relates to the interior light switches. I don't think my Chilton has enough detail in the wiring diagrams to pinpoint this. But....maybr they do share a common ground somewhere?

[mishalah]

From looking at the schematic for interior lights, the most probable culprit seems to be the interior light control (rheostat). Because the lights on the stereo are also dimmed by that control there is a direct wiring link between the radio and the rheostat (along with all the other instrument lights). SOoooooo...unless I can clean the switch from outside, or by simply pulling the switch panel forward, I'll probably have to R&R the switch. Hopefully I can do it with spray contact cleaner and air pressure.