1999 GMC Sonoma Electrical problem

[twdgs86]

Hello everyone,
I have a 1999 GMC Sonoma with some issues!
When you first start the truck it will have none of the warning lights on other the ones that always come on at start up.
But if you turn on the headlights the radio will turn off then will come back on in a few seconds,will not lose its time or any presets. Then the ABS,Security,Airbag and seat belt warning light will come on. It will do the same thing if you use the headlight dimmer switch or the interior light switch. The headlight switch was just replaced to get the instrument panel lights to work.
Any help on where to start looking or what could cause this is greatly appreciated.

 

[greg409]

I've found that often when bizarre electrical behavior happens like your's or turn in A/C & wipers start, it often is result of a bad ground.

Electrical always follows the path of least resistance.

You might scrounge up a haynes (or equivalent) shop manual with wiring diagrams - It's usually labor intensive, you may get lucky.

I'd start by checking/cleaning the dozen or so ground connections.

luck,greg