89 Suburban 5.7 blowing fuse #5 GAGE/IDLE

[89v1500]

Howdy!

I recently purchased a 1989 GMC Suburban V1500. It has been off the road since sometime around 2006. Just got it back up and running with a new fuel tank, pump, and injectors. Quickly noticed that the gauges didn't work! Checked the fuse and it was blown. Tried putting another one in and the gauge lights came on, but as soon as I cranked up the truck I heard a "POP" and gauges were dead again. I've tried unplugging a couple components to see if the fuse would stop blowing, including the gauge cluster, warning buzzer, brake switch (torque converter clutch solenoid?), and one module thing that connected to a screwed-down plug butted up against the speedometer cable on the gauge cluster. None fixed the issue. I found a wiring diagram but I'm having a hard time following it. The gage/idle fuse feeds a pink/black wire, circuit 39, but so does fuse 4 right above it, labeled ignition! Could there be an issue with the ignition circuit that is causing a different fuse to blow? I know there is a short to ground somewhere just having a hard time finding it. Would feel much more comfortable to run the truck if I knew what the oil pressure was and the engine temp (although I'm sure these gauges are not very accurate).

Does anyone have an idea on things to check for? Or has anyone experienced the same issue and found a solution? Any ideas would be a huge help. Thanks!

 

[gmbellew]

1990 suburban Gage/idle fuse circuit shorted

driving today and all of a sudden had no gauges. ECM was still reporting all the right data - coolant, vss, volts (although volts were lower than normal), etc. also noticed that when I turn the lights on, the buzzer buzzes....bc it thinks the ignition is not on. found the gage/idle fuse blown...

www.gmsquarebody.com

 

[89v1500]

1990 suburban Gage/idle fuse circuit shorted

driving today and all of a sudden had no gauges. ECM was still reporting all the right data - coolant, vss, volts (although volts were lower than normal), etc. also noticed that when I turn the lights on, the buzzer buzzes....bc it thinks the ignition is not on. found the gage/idle fuse blown...

www.gmsquarebody.com

Thanks! The purple wire that you speak of, did it get worn through in the dash or near the transmission? Will definitely try to look for that tomorrow. I unplugged the brake switch earlier today and thought I found my issue. The gauge fuse didn't blow until the suburban ran for about two seconds. Usually it would either blow when I turn the key to ON or during cranking.

 

[gmbellew]

Thanks! The purple wire that you speak of, did it get worn through in the dash or near the transmission? Will definitely try to look for that tomorrow. I unplugged the brake switch earlier today and thought I found my issue. The gauge fuse didn't blow until the suburban ran for about two seconds. Usually it would either blow when I turn the key to ON or during cranking.

by the transmission. driver side. rubbed on the bracket before the TCC solenoid switch.

 

[89v1500]

by the transmission. driver side. rubbed on the bracket before the TCC solenoid switch.

Found a purple wire near transmission (goes to a sensor or something, I assume that’s the solenoid switch) , but I don’t see any brackets. Looks like it’s just a harness that runs up to the engine bay somewhere. Am I looking in the right place? Hard to see, but one of those wires is purple. Lol. Thanks so much.

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[gmbellew]

Mine was rubbed through on this bracket right above the TCC connector in the photo.

You might just move the harness a little to make sure it isn't touching metal and see if that helps you narrow down the location. I think there is also a bracket by the firewall where the harness leaves the cab...could be an issue there also.

 

[89v1500]

Hmmm! I believe that's the same harness as the one in the picture I took. Doesn't appear to be any breaks at least closer to the transmission. Kinda hard for me to see where it goes when it gets closer to the firewall, but I wiggled it around a little and tried to make sure it wasn't touching metal anywhere. While I was digging around near the distributor I found this black wire with a spade connector on the end. Pulled it out and just let it hang somewhere out of the way, thought it was the same purple wire at first. Put a 20 amp fuse in the gage idle slot, and it didn't blow! So, I'm not really sure what "fixed" it. According to my multimeter the black wire is a ground so I don't think that was the fix unless it was touching a bare wire somewhere. Tried wiggling the purple wire again to see if the fuse would blow but no such luck.

Glad the gauges are working now, but I hate that I didn't find the problem. Definitely narrowed it down though! Will try to investigate a little more and see if I can find a nicked wire. If so I will report back. Thanks!

 

[gmbellew]

I'd guess that your manipulation of the harness moved the purple wire off it's short to ground for the mean time. Go out at night and use a flashlight to inspect that wire. The rub through will be fresh and shiny metal compared to everything else, and will be very reflective.