Random brake pedal electrical issues

[Upthebeach]

Hi All,

Hoping to get some leads on how to track down some electrical issues I am having. For a bit of background...1996 GMC Yukon, 2 door. 460,000 miles.

In the past two years I have replaced the brake pedal switch (this week), the A/C and heater control switch/panel (18 months ago), turn signal switch (2 years ago), blower motor/relay and resistor in the past year, both tail light circuit boards last week.

Issues:

With the truck running...

With my foot on the brake, in park, turn off truck and remove key. Truck continues to run until I take my foot off the brake. Then it stops running.

Brake lights always stay on. Left directional works, right directional turns on but no flash. Use to happen only when the truck was cold and would return to normal after 30 minutes or so. Now it does not 'fix itself.'

Climate control fan only works on high, which happened a few years ago. Replacing the A/C control panel fixed this. Then it broke again.

(On a side note, with the fan blowing on high very little air comes out of the vents. Maybe a clogged evaporator core?)

The turn signal switch I replaced because the headlights only worked on high beam.

With the truck turned off...

If I step on the brake pedal the dash warning lights come on and it sounds like a small motor is turning/buzzing.
A youtube video I saw with this same problem said he resolved this by replacing the turn signal switch.
If that is true, then the turn signal (maybe twice) and A/C control panel failing (twice) is a symptom of a deeper issue. Which I would like to resolve so I don't keep having to buy the same parts over and over. Besides who knows what will get fried next.

Maybe of importance...I drive often and have a small inverter charging my laptop. The cigarette lighter sockets must get too ho, they get hot when they start to not charge my laptop properly, as every two years or so I have to replace the cigarette lighter sockets.

Thanks,

Mike

 

[east302]

Here’s a similar thread with the engine shutoff issue. It was the hazard switch (turn signal assembly) in his case:

Electrical issue

I have a 98 tahoe 2wd. It has an electrical issue i can't seem to find. My right turn signal does not flash and my brake lights stay on when the key is on. I have replaced the brake light switch, flasher and even the rear brake light assemblies. What makes it more strange is that i can shut the...

www.gmt400.com

As for the climate control, is your connector at the blower switch melted?

 

[Upthebeach]

Thanks east302. I read through that thread you mentioned. I suspect it is a bad turn signal switch.

But why is that breaking? When I replaced it I replaced it with AC Delco (not saying that is the highest quality these days, Hecho en China!).

And is my broken A/C control panel (also AC Delco replacement) also being caused by the same problem?

In other words, what is causing the new parts to fail? I don't want to be replacing these parts every two years. And who knows what will fail next.

I also forgot to mention...I never really paid much attention to the volt gauge, but seems to me it was always in the middle, right at 14.
Now it is a notch or two below 14, brand new battery and very little decrease when lights/fan/radio are on or off.

I feel like there is a bad ground or a short somewhere in the system.

Possible from all the charging I do for my laptop from the cigarette lighter. And sometimes I let the computer charge up for 30 minutes after the truck is turned off.

Thanks again!

 

[Upthebeach]

When I replace the a/c control panel I don't remember seeing any melted wires. But have heard you should replace the harness along with the panel.

Again though, what is causing the wires to melt...if they are?

 

[east302]

For new parts, it’s a chance no matter what you buy. Odds are usually better with Delco parts, but even they have issues sometimes. Often, a 20-something year old GM part that has been through a fire, flood and acid bath will work better than some of the stuff (rhymes with Floor Man) that is sold these days.

The hazard switch failure in that other thread was likely a mechanical issue - the little switch pins just broke after a couple of decades. You would expect that a new part would offer a comparable lifespan but, well…

On that blower switch, it’s the connector that melts and you’ll know it when you see it. The plastic gunks up the pins on the blower switch and operation gets flaky. Someone else could probably elaborate on why it’s an issue, but my guess would be water dripping down through the cowl screw, rusting out the blower and causing an issue there when it’s running and taking greater effort to do so. All three of my 98s have had the connector replaced. I used this:

You must be registered for see images attach

If your connector checks out, pull the connector at the resistor and see if you’re getting battery voltage from the control panel (at each fan speed) as this then sends power through the high speed relay. As-is, it sounds like you’re just getting battery voltage (circuit 542) so either the relay is stuck or isn’t getting voltage from the resistor - either because the resistor is faulty or it isn’t getting voltage from the control panel due to an issue with the blower switch itself or that connector.

Blower switch can be replaced independent of the control panel, but if it’s just a melted connector then replace the connector and scrape the plastic off of the switch pins.

It’s all grounded through the ground wire attached to the blower, so it doesn’t sound like a ground problem since it works on high.

You must be registered for see images attach

 

[Erik the Awful]

Factory cigarette lighter sockets are junk, and replacements are even worse. I'd make a separate pigtail for charging the laptop with some XT60 connectors. I don't think this is your ultimate issue, but I wouldn't want your truck to burn down.