I have a 1990 B2600 and there is an electrical issue that's driving me crazy. I hopped in it a few days ago and turned the key and nothing happened. No dash lights and nothing to the starter. I checked the battery with a multi meter and 12.7 volts I raplaced the 80 amp fuse in the fuse box beside the battery and still nothing. While trying to figure this out I found hazard lights, head and tail lights and horn are working. Today I removed the ignition switch and checked continuity with a multi meter it seems to be working fine. While I was under the dash I checked all plugs on the wiring harness that go to the ignition switch and nothing had power. Is there a fusible link between the fuse box (beside the battery) and the ignition switch or what the hell am I missing. Any assistance is greatly appreciated. Cheers Ken

 

This is obviously where to start. Here's the wiring diagrams that are relevant to your issue.