NEED HELP AC / Heater Blower working intermittently with dash lights

[Xodus989]

Hello everyone! I just moved to Michigan and bought an 05 Envoy from a friend for 800 bucks. Everything works great except quite often the dash lights up and the blower motor stops. Once I've seen all the guages besides speedo and tach go to zero. After a little research I found ground junction G102 was the most likely culprit. I pulled it out tonight and there was little to no corrosion or rust. I wire brushed both the metal connector and the bolt to make sure I wasn't missing anything. I slathered it all up & the threads with dielectric grease and put it back together with the same results. Nothing changed.

I'm 99.9% sure this has to be a ground issue with it's intermittency and multiple system involvement. I can confirm when the ABS light is lit up the ABS no longer works too. I've attached two pictures. The first is the dash with all the lights that are on when things aren't working (when they do work, only the CEL light & every once in a while the change engine oil and service 4WD light come on). The second is G102 after I cleaned it up.

Where should I start looking to next? Is it possible the corrosion is *inside* the plastic connector? Thanks for any advice!

 

[Mooseman]

Electrical weirdness like this I always start with the ignition switch.

 

[TequilaWarrior]

Electrical contact cleaner will be your friend when cleaning anything like grounds...

IF there was some "shmutz" in the connector, a spray out with contact cleaner should've cleaned it up... but it's not likely to be unclean...

There are myriad electrical grounds... and "cross talk" from one ground to another is not unheard of. A bad ground at a corner light will cause a headlight to not work and the corner light to glow steady... all kinda weird stuff. There may be multiple grounds that serve the dash... check 'em all if there are. I know complete schematics are available on this site... they might even be in @Mooseman signature block.

FUSES.... loose fuses are as bad as a flaky ground.... I've had a loose fuse randomly light my whole dash up and kill the engine while driving down the road... I was baffled and took it to a dealership and the tech took less than 5 minutes to find a "wiggly" fuse... a quick bend of both fuse legs and it's never done it again.

The fact that it affects the dash and the blower simultaneously suggests a connection of some sort that these two components share. If I understand your post correctly, this thing runs and drives while this is acting up... right? If so, that would steer me away from the PCM and stuff like that, but lean me heavily to a near dash ground... there's another ground near the ABS pump, too.

 

[Xodus989]

Electrical weirdness like this I always start with the ignition switch.

What do you mean with this? I haven't done too much electrical in vehicles outside of wiring radios and a few aftermarket accessories.

Should I check the ign switch ground to g201, because there is a pin for it at that junction.

Electrical contact cleaner will be your friend when cleaning anything like grounds...

IF there was some "shmutz" in the connector, a spray out with contact cleaner should've cleaned it up... but it's not likely to be unclean...

There are myriad electrical grounds... and "cross talk" from one ground to another is not unheard of. A bad ground at a corner light will cause a headlight to not work and the corner light to glow steady... all kinda weird stuff. There may be multiple grounds that serve the dash... check 'em all if there are. I know complete schematics are available on this site... they might even be in @Mooseman signature block.

FUSES.... loose fuses are as bad as a flaky ground.... I've had a loose fuse randomly light my whole dash up and kill the engine while driving down the road... I was baffled and took it to a dealership and the tech took less than 5 minutes to find a "wiggly" fuse... a quick bend of both fuse legs and it's never done it again.

The fact that it affects the dash and the blower simultaneously suggests a connection of some sort that these two components share. If I understand your post correctly, this thing runs and drives while this is acting up... right? If so, that would steer me away from the PCM and stuff like that, but lean me heavily to a near dash ground... there's another ground near the ABS pump, too.

I've noticed it does affect more than just the blower today. ABS is disabled as well as cruise control.

I downloaded the wiring diagrams and while I can understand what they mean, I have a hard time knowing what to check outside of the end of the line connections.

Like with g201, it powers a number of accessories, some work and some don't, so should I follow the ground on the diagram until I get back to the battery / body grounds and keep checking voltage on those?

All my tools are back in California so I can't do too much right now, but I'll be picking this up tomorrow so I can really start diagnosing.

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[Mooseman]

What do you mean with this? I haven't done too much electrical in vehicles outside of wiring radios and a few aftermarket accessories.

Start by just replacing the ignition switch. It's a common failure part that can cause all sorts of electrical gremlins. Or check the switch to make sure it is working correctly.

 

[Xodus989]

Will do, It's going to be a few days or a little over a week before I get back to this thread. I have a final interview for a job next week and will have some income finally so I'll be able to start really working on things.

 

[Mooseman]

Good luck with the job!

 

[Xodus989]

Thank you! Is there a way to test the ignition switch without replacing it? I don't want to spend 45 bucks on it if I don't have to.

 

[Mooseman]

Check for a YT video by South Main Auto. He shows it very well.

 

[Xodus989]

Great news! I replaced the ignition switch and everything seems to be working now. None of the lights on the dash are illuminated anymore (that shouldn't be).

The rear air vents and front forward facing air vents still don't blow, but all the other vents seem to work properly. Luckily the defrost blows so hard you don't really need the big front ones 🤣