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Hello, I’m new to ETCG Forums. Actually I only just found Eric’s Youtube last night. Great videos and yes, I watched the electrical ones.
Here’s my story, I’ll try to shorten it as much as possible. Hopefully one of you will have an “Oh, I know what you’re talking about” moment. Anyways, here we go:
Quick Background:
88′ GMC Suburban been sitting dormant for ~3 years. I’m working on restoring it. It’s a 5.7L 350 2WD.Oh, and yes, I have checked all the fuses first and it has never been in any major collisions that I know of or can see evidence of.
So, the Power windows don’t work. First I took off the door panel and tested the switch, fine, removed the motor and regulator and tested the power cable. Got around .01-.03 volts. Hmm, that can’t be good. Tested the power at the switch and it was getting about the same, further implies that the switch is probably fine. Found the fuse(Circuit Breaker) for the PWR Windows and lo and behold there’s no power getting to it. Turns out, whole 3rd column in the fusebox is without power. This explains my heater and AC not working either.
So, I then remove the big connector on the engine side of the firewall that connects to the fusebox. That had a bunch of 25 yr old dielectric grease in it which I cleaned out with CRC cleaner because the terminals were dirty as heck(I mean, baaadddd). Then checked all those terminals for power. Two of them are getting 12.6v. Should there be other terminals receiving power?
Checked the other wires in the engine compartment as well as I could and couldn’t find any broken or frayed wires. I went under the car today and looked at the starter. The power wire from the battery to the starter has a little insulation off and the bare stranded wires are showing but the starter works just fine. Also found a Red 3.0 SQMM Fusible Link there. Some of the outer insulation was cut but there seemed to be inner insulation that was still intact. Checked continuity back to the fusebox connector and it seemed good. Could that relay still be the culprit?
So, that’s about where I’m at.
Yes, my battery is good. It’s 6 years old but it is good(it was not in the car the past 3 yrs).
The car starts and runs fine, it’s just this 3rd column on the fusebox seems to not be getting power.Now, I also know I have a loose cable somewhere in the starting system. How do I know this? Occasionally if I jiggle some of the wires around the air filter pan the car won’t start. If I jiggle them again it will. When the car doesn’t start because of this it will still make the BEEEE sound with the key in run and will then make one click if I try to crank it. After that it does nothing until I jiggle the wires again.
If I don’t touch those cables the car starts reliably.So, I know I have a cable problem somewhere aside from the power windows/AC/heater problem. Any ideas on where to look/what to test? As summer is fast approaching here it would be a tad more pleasant for me to have my AC or power windows working(preferably both :D!).
I should also note that we have an identical Chevy Burb. Same year and everything. It’s heat and Power Windows work. I’m going to compare some wiring and things between the two tomorrow. Dad uses it as his daily driver so I can’t test it during the week.
If you need any more info just ask and I’ll be glad to give it as best I can.
Any help would be extremely appreciated.
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Replies
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If power is missing to part of the fuse box.Then its
from the battery source to the fuse box.Have you checked
for fusible links? here is a sight for a wiring diagram.Yesterday I checked the fusible link connector to the Starter solenoid. The positive from the battery connected to this same bolt. The eyelet on the link was a little dirty so I filed it clean and put them back together and tightened it firmly. I didn’t start the car yesterday.
Today I checked the power in that fusebox connector and everything has power that it should. I checked our identical Chevy Burb that works and all the same pins had power. Previously my GMC only had power to 2 pins. So Apparently that fusible link must not have been getting a good connection.
After reconnecting things I tested on the fusebox side again. I got .01-.04 on the 3rd column fuses whether the key was in, on Accessories, or the car running. When I did the same test on the operating Chevy I got .01-.07 without the key but got a full 12.4v with the key on Accessories or 14+ with the car running.
So I’m thinking there might be an issue in the key switch or ignition switch preventing power from being sent to the accessories?
BTW, those diagrams are helpful, thank you.
Well, I got it out today and lookie what I found!
Obviously I’ll be replacing that switch and probably the connector too(got to clean it at least).
I have confirmed this powers the Heater, Aux Heater, AC, and Power Windows. It also looks like the original 25 year old switch. What could have caused it to burn like this though, just age?
YIKES ! It’d be really swell if you could find that part of the schematic for that entire circuit including it’s branches. It appears that you had a short to ground of some kind somewhere in that circuit and that caused the connector to overheat and melt down. If you can find the schematic, even if you have to blow it up on a copy machine to read the thing, see what the voltage readings should be on which wires in that circuit with the key off. Test it. I’d look for an overload first or see if you can find a shorted ground in that whole circuit. Having a power probe to test for hot and ground would be real helpful. And before you start testing, make sure that circuit is opened at the shorted connector and trace it back to the main panel. Otherwise you might end up chasing your tail.
YIKES ! It’d be really swell if you could find that part of the schematic for that entire circuit including it’s branches. It appears that you had a short to ground of some kind somewhere in that circuit and that caused the connector to overheat and melt down. If you can find the schematic, even if you have to blow it up on a copy machine to read the thing, see what the voltage readings should be on which wires in that circuit with the key off. Test it.
You probably have have found your problem but before you just go with a new connector down there, it’d sure be nice to know what caused that connector to toast. Make sure you don’t have any shorted grounds on that circuit or the whole thing might light up all over again. A meter or power probe will do fine. Test voltage levels at connectors like heater switches, blower motor and just pop out the window switch and measure the juice at the contact under the switch with the ignition key on but engine off. Check too for wiring problems behind the radio or where old electronic accessories were hooked up at some time and then removed.
Electrical problems can be a real pain but a methodical approach should help prevent you from chasing your tail. Be patient but be thorough. Good luck.
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