s10 Strange Electric/Guages/lights problem

Sounds like alot of us are replacing heater cores, I wonder why? After I put everything together again, I have a weird combination of electrical problems involving the lights, dimmer switch, door switches, all guages and radio.
1) engine on, LIGHTS OFF, doors closed- radio on and can control all guages with dimmer switch. 2) Engine on, LIGHTS ON, doors closed- radio dies, still control all guages with dimmer switch, PLUS directional lights and high beam indicators on. 3) Engine on, LIGHTS OFF, DOORS OPEN- radio works, still control the guages with dimmer switch.

After reading some of the previous threads, I looked for bad/missing grounds and I can't locate anything amiss... Anybody got a suggestion? Thanks alot, I'm beyond my diagnostic level now.

Sounds like alot of us are replacing heater cores, I wonder why? After I put everything together again, I have a weird combination of electrical problems involving the lights, dimmer switch, door switches, all guages and radio.
1) engine on, LIGHTS OFF, doors closed- radio on and can control all guages with dimmer switch. 2) Engine on, LIGHTS ON, doors closed- radio dies, still control all guages with dimmer switch, PLUS directional lights and high beam indicators on. 3) Engine on, LIGHTS OFF, DOORS OPEN- radio works, still control the guages with dimmer switch.

After reading some of the previous threads, I looked for bad/missing grounds and I can't locate anything amiss... Anybody got a suggestion? Thanks alot, I'm beyond my diagnostic level now.


i would invest in a manual with a good wiring diagram of the dash and locate and secure all the grounds, it definitely sounds like a feedback issue. MIGHT have pinched some wires together. and heater cores are like anything else, the cheaper GM can get em the more they buy. At least theyre easier to change on GM than chrysler vehicles. the caravans you have to take the dash OUT and take the ENTIRE heater box assembly out which includes the ducts and everything to replace the heatercore and they seem to go out a lot.

i would invest in a manual with a good wiring diagram of the dash and locate and secure all the grounds, it definitely sounds like a feedback issue. MIGHT have pinched some wires together. and heater cores are like anything else, the cheaper GM can get em the more they buy. At least theyre easier to change on GM than chrysler vehicles. the caravans you have to take the dash OUT and take the ENTIRE heater box assembly out which includes the ducts and everything to replace the heatercore and they seem to go out a lot.


Could be a bad dimmer switch. I know sounds crazy however, I have a 91 Blazer s-10 and have an electrical dashboard, and when ever i would close the car door all the dash lights would go dim, all the readouts except the temp would drop to zereo and my radio would shut off.

Open the door and they would all read normal again. Got a switch panel off of e-bay for 22 buck and it worked like a charm.

one thing to check is the rear wiring harness where it passes under the drivers foot(on early models). I'v had this harness play havic(wires warn through) with my system(guages dome turn fuel etc)until it started blowing fuses after 3-4 days.