I have an 89 gmc s15 2.8 l v6 and my gauge lights qiut working and the fuse is blown in the ign/gauge slot and I replaced it with all size fuses and when I would turn the switch on it blow the fuse and I dont have the time to spend hours chasing wires just trying to narrow it down ive spent alot of time under the dash and under the hood in the past just replacing parts im usually really good at diagnosing stuff but for some reason this just has me stumped any suggestions would be great

 

Customer Concern - The IGN/GAU fuse will pop as soon as the key is turned to the run position.

1. Locate the bulk head connector C100 on the driver's side near the brake booster. Remove the Pink/Black wire from cavity B2 and then plug the connector back in.

2. If the fuse still pops with the Pink/Black wire removed from connector C100, unplug the Cruise Control module, rear defogger switch, rear defogger relay, Daytime Running Lights (DRL), Instrument Panel Cluster (IPC) and rear view mirror and retest.

3. If the fuse still pops, locate splice S200 near the steering column above the brake switch inside of the wiring harness. Disconnect the wires from S200 one at a time while testing the fuse.

4. If the problem is gone when one of the wires is disconnected check that wire using an ohm meter to each of the devices unplugged to locate what the wire powers up, and then check the wire from S200 to that electrical device for short to ground.

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The IGN/GAU fuse powers up the following electrical devices:
Cruise Control
Instrument Panel Cluster (IPC)
Rear defogger switch
Rear defogger relay
Daytime Running Lights (DRL)
Rear view mirror
Generator
Variable tuning control relay
Oxygen sensor
Transmission
Convenience center

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i had the same issue with my 1993 s10 blazer years ago. i couldnt find any of similar complaints to your year. mine used to just blow out every 4 hours or so so i just keep changing it. what sucks is theres a ton of things on that one fuse. so if your rear view mirror has lights on it it could be a bulb causing it.