I just bought a used 91 GMC Sierra pickup. 350eng, auto It runs well for it's age, and I like the extended cab and full bed. It has a few issues mostly with the wiring. For one thing, the heater fan wires were disconnected from the speed switch, and someone used a regular house light switch for on-off (hi speed) only. Well, ok, that works but I'd like to find out if there is a common problem with those original switches.
I also got a passenger side door switch that does not shut off the light unless I duct tape a piece of cardboard on the door. I know the old metal switches could be pulled out and lengthened. Is there a way to do the same with these newer plastic ones? If not, how do I remove the whole switch, does it just pull out or what? light is for the both the regular brakes and parking brake
And finally the actual topic of this message. The red brake light is on most of the time on the dash. The brakes work perfectly. I made sure the parking brake was completely off, and pulled it upward rather aggressively. The light stayed on. I'm thinking that the problem is not the brakes, but the sensor. There is a plug on wire on top of the master cylinder. Is that the sensor for the brakes? Is there a way to test that sensor? Yes, the brake fluid is FULL. OR The truck had the original owners manual, and it says that same brakelight is for the parking brakes. Where would I find that switch? Maybe that one is stuck. I know to unplug that one to see if the light goes off. I just need to find that switch.
Anyone got any ideas?
Is there anywhere online to get a wiring diagram for this truck?
Thanks to all.
LM