no park lights,dash lights or warning buzzer

Hey guys,
I have a 1989 GMC sierra.One day the dash lights,park lights and the warning buzzer that tells you your headlights are on all stopped
working at the same time.Fuses are good. Do you think it could be the headlight/parklight/dimmer switch? What do you think it could be?
Thanx.
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I just had the same problem - turned out to be a short in my trailer wiring harness. I 'thought' the fuses were good, but although it looked good it was actually bad. I put another fuse in it's place and saw a little flash when the new fuse blew. At first I suspected the headlight switch or the multifunction switch in the column... turned out it was neither.
My truck is a 1996, but the premise is the same. I disconnected the headlight switch from it's connector. To isolate the problem I found a connector at the back of my truck behind the bumper that goes to the tail lights and disconnected it. I also found a connector under the hood of the truck close to the ABS module/underhood fuse block that goes to the front lights, and I disconnected that as well. Then when I checked for shorts at the headlight switch connector and found none. I plugged in a new fuse, and the headlight switch, then my dash lights and warning buzzer were working. I plugged in the front running light harness and they worked as well. With the problem isolated to the rear lights/harness, I started looking for shorts and found my trailer wiring harness to be the problem. I connected the rear harness without the trailer wiring and everything was working great. I threw that harness in the trash....
Don't discount the headlight switch though. I have had to replace the multifunction switch in my truck twice in the past 6 months, so I don't think a bad headlight switch would be out of the question. It's tough to stomach the $$ the dealer wants for the electronic parts, especially since they are non-returnable - so you cannot just buy a new switch, try it out, and if that's not the problem then take it back for a refund. If you are savvy with a 12 volt trouble light or a multi-meter then you can save yourself some $$ by troubleshooting.
Hope this helps. SuperDave
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It was the switch.Thanx guys.
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