Random electrical issues

[Upthebeach]

Hi All,

Thought I'd reach out to the forum and see if anyone has had similar problems on their truck and suggestions on how to fix them.

I drive a 1996 GMC Yukon 2 door, 450,000 miles.

The most recent issue is the brakes lights being on without pressing the brake pedal. And while this issue is happening the right directional turns on, makes a horrible buzzing sound but does not blink. After the truck warms up (I am in New England and not sure if this is air temperature related and not exactly sure at what point this issue goes away) the brake light will go off and the blinker will work as normal.
About a year ago I replaced the directional stick.

Another issue is fan speed control knob. It only works on the high speed, which I have read here on the forum is the default setting when the others do not work. This first happened about two years ago. I replaced the blower motor, the resistor and the.....none of which fixed the problem. Then I replaced the whole AC control panel. That did fix the problem. The fan worked fine for a year and now, again, the fan only works on high speed.
It seems to me that it is not the control panel that is the problem. Rather something is causing the fan speed knob to fail.
Any ideas on what could cause the fan speed knob to fail?

Another issue is the passenger side headlight. It works, but is rather dim. I have read somewhere that is could be a bad ground. But I am not sure where the ground is located to clean it up.

Is it normal for the fan speed to vary with the engine rpms?

One other issue I'll touch on quickly, and not sure it is an electrical issue. I tried to turn my truck off last week but the truck did not stop running. Key was out and I tried putting the key back in a few times with no luck.
By the time I got home it did turn off. It only happened once so far.
Any suggestions on that fix? And if it does happen again how would I get the engine to stop running???
Possible a worn out key? Or maybe the truck need a new ignition lock cylinder?

Much thanks!

Mike

 

[east302]

Another issue is fan speed control knob. It only works on the high speed, which I have read here on the forum is the default setting when the others do not work. This first happened about two years ago. I replaced the blower motor, the resistor and the.....none of which fixed the problem. Then I replaced the whole AC control panel. That did fix the problem. The fan worked fine for a year and now, again, the fan only works on high speed.
It seems to me that it is not the control panel that is the problem. Rather something is causing the fan speed knob to fail.
Any ideas on what could cause the fan speed knob to fail?

The blower switch itself (under the panel’s fan dial) is replaceable. I’ve gone through three on a new Delco GM panel purchased a year ago.

See if the harness that connects to it is melted.

 

[Upthebeach]

East302,

Thanks. I recently came across information stating that knob is replaceable. Would you know the part number? I looked on RockAuto but could not locate it, probably because I do not know its technical name.

I see the knob failing as a symptom of a bigger problem, what is causing it to fail over and over?

Thanks again!

 

[JWOK]

Hi All,

Thought I'd reach out to the forum and see if anyone has had similar problems on their truck and suggestions on how to fix them.

I drive a 1996 GMC Yukon 2 door, 450,000 miles.

The most recent issue is the brakes lights being on without pressing the brake pedal.

One other issue I'll touch on quickly, and not sure it is an electrical issue. I tried to turn my truck off last week but the truck did not stop running. Key was out and I tried putting the key back in a few times with no luck.
By the time I got home it did turn off. It only happened once so far.
Any suggestions on that fix? And if it does happen again how would I get the engine to stop running???
Possible a worn out key? Or maybe the truck need a new ignition lock cylinder?

Much thanks!

Mike

Check your brake light switch. I ran into an issue on a 96 Tahoe where the engine would not shut off intermittently because one of the contacts in the brake switch had broken loose and would sometimes fall across the other contacts and feed power back through the ignition switch. Especially as you already have brake light issues I would say this is quite likely.

 

[GoToGuy]

The headlight, if you follow the bkack wire off the headlight bulb each side grounds to the inner fender. Right side near the battery. Left side inner fender or radiator support. Both are within 24 inches of headlight. Clean fender surface, terminal eye could have corrosion at crimp attachment. Good luck.

 

[GoToGuy]

A good idea if your going for million miles. Why not? Is get OE manuals here. Make life easy for simple fixes.
The engine not shutting down with key turned to off. Key is lock and tumbler moving a rod down colum to activate sliding electrical switch on lower colum above your shins. For starting, run position, shutdown. First thing I'd check are the key tumbler and rod moving together. Good? Then move to test ignition colum switch. Good luck.

 

[JWOK]

A good idea if your going for million miles. Why not? Is get OE manuals here. Make life easy for simple fixes.
The engine not shutting down with key turned to off. Key is lock and tumbler moving a rod down colum to activate sliding electrical switch on lower colum above your shins. For starting, run position, shutdown. First thing I'd check are the key tumbler and rod moving together. Good? Then move to test ignition colum switch. Good luck.

I believe you are thinking of the earlier column with the rod and sliding switch. 96 would have the rotary style switch located by the tumbler and is connected by a pair of gears.

I would agree with you on checking the ignition switch as part of proper diagnosis. I only offer the suggestion of checking the brake switch first given the combination of symptoms, having run into something similar which was a pain in the rear to diagnose, and the ease of checking the brake switch.

 

[Upthebeach]

At this point, I might as well just start replacing things that a acting weird for the first time.

Brake light switch and ignition to start

I'll follow the black wires and check the ground. Nice to know which wire to trace.

Thanks

 

[east302]

East302,

Thanks. I recently came across information stating that knob is replaceable. Would you know the part number? I looked on RockAuto but could not locate it, probably because I do not know its technical name.

I see the knob failing as a symptom of a bigger problem, what is causing it to fail over and over?

Thanks again!

Most chain parts stores should have it but you may have to steer them in the right direction. The gray knob just pulls off. On mine, the wiring connector had melted, so see if you have any damage there and if you have any rust on the blower shaft itself (leaking cowl vent screw letting rain fall down into the blower housing).

Here is the blower switch on rockauto for my 98:

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