Wiring issue or brake issue?

[RSchwarzli]

So I pulled my dash apart to pull out the heater core box a few weeks ago. Since I did that, my brake and abs light has come on. For the first few days it was intermittent. Now it is on steady.



Then with a 3/4 full tank, the low fuel light came on! Did that a few times, and then not again. Fluke? maybe.



Thoughts? It sounds like it is a ground issue as they both run off the same ground circuit.



Is there a ground strap under the dash that I forgot to connect? The flat silver one off the radio is connected... .



Help! Its buggin me like a flea on a dog!



Robert

 

[hcole]

Robert, I had a 91 that did this and a couple of other things I don't remember. I had ABS light and brake light and it would blow a fuse (can't remember which one) about once a week. This went on for several weeks while I tried to chase it down while still driving it. The ABS brake module is right behind the glove compartment. Take the glove box off, 3 screws on the hinge I think and it's right in front of you. I found nothing there or on the rear end sensor bad. I stumbled across MY problem changing the oil one day. The harness on the cowl above the valve cover had sagged down and was rubbing on the valve cover. The vibration of the engine had rubbed the outer covering of the harness through and had begun working on the wires. The ABS wire was one and it was only looking for a ground to turn on. There were several involved and one would occasionally blow a fuse. This harness carries just about everything on the truck. Check it out. Hope this helps.

 

[RSchwarzli]

Hmmm. Will check the harness.

So many possibilities. I had the engine wiring moveing around, brake/abs module was removed for heater box removal, half the dash was tampered with, some wires were unplugged and replugged.....

Grrrr. I hate misc electrical issues.

Thanks for the thoughts!

 

[HHhuntitall]

Ahh, isn't the ABS module screwed to the firewall? Doesn't it have to be grounded through it's mounting bolts, like the voltage regulator?

 

[RSchwarzli]

Hmmm. You might have hit the nail on the head. I put RTV on the screws to seal any potential leaks through the cowl..... I wonder... ...



I did not think it was grounded through the screws though. The service manual shows a wire off the back of the dummy light cluster. Same one that feeds all the dummy lights.



Worth checking screws though... .

 

[HHhuntitall]

And after thinking about it, I had one a while back that the Wait to Start and Water in Fuel lights would work sporadically..... a little dialectric grease seems to keep the ghosts away. I think dust and vibration have done their number on the contacts, so a little help was needed..... the round connector didn't feel loose, but being as the poles are round, if they get worn from moving around too much.....

 

[RSchwarzli]

Good point. I have had the round connector on and off close to 20 times last few months... .

 

[Paychk]

I think the grounds maybe at fault check the grounds just to the right of the steering colum there are two.



One runs up to the radio but there should be another next to it.

 

[RSchwarzli]

Ahh, isn't the ABS module screwed to the firewall? Doesn't it have to be grounded through it's mounting bolts, like the voltage regulator?

OK. Tried that. No change.

I think the grounds maybe at fault check the grounds just to the right of the steering colum there are two.



One runs up to the radio but there should be another next to it.

Thanks for the pic! That is great!



Did check it. Play with it. Was OK. Still no change as the light is still on! #@$%!:{

 

[HHhuntitall]

Hmm, have you checked the ground wire on the battery to Chassis side? I don't think that'd be it, but I've seen that cause ghosts on the 2nd gens... ...



And have you checked the rear field generator in the top of the rear diff housing? Or do you have one on the '90? Are the two wires making it all the way back there, or do you have 'em?

 

[RSchwarzli]

Yes, I believe I have them. And my truck was just in for oil spray the day before I noticed the light... . hmmm. I wonder if they put that wand in a area they shouldnt have... . will do some under truck checking.

 

[JDiehl]

There is also a ground on the fire wall directly behind the #6 valve cover.



Just cleaned up the grounds and it cleared up my erratic gauges and pulsating light issues.



Might be worth a try.

 

[RSchwarzli]

THAT could make sense. I believe I has alot of that disconnected for blower motor cover removal.