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Water temperature gauge pegged- 1991 Chevy Suburban

Discussion in 'GM Electrical Tech' started by Crawdaddy, Jan 11, 2014.

  1. Crawdaddy

    Crawdaddy Epic Member Staff Member 5+ Years 1000 Posts Platinum Contributor

    The water temperature gauge is pegged out all the time on my 1991 Chevy Suburban. The gauge reads far past the max scale reading even when the truck has been off for multiple days. I disconnected the single-wire connector from the sender on the drivers side head and even that doesn't cause the gauge to change. I'm going to pick up a 220 and 150 ohm resistor to build tool J-24538-A listed in the factory service manual (http://coloradok5.com/forums/showthread.php?t=263131). Hopefully I don't have to pull the gauge cluster and repair it or get it repaired since it's a pain to pull. Any ideas what's going on and how to troubleshoot it and fix it?
  2. Crawdaddy

    Crawdaddy Epic Member Staff Member 5+ Years 1000 Posts Platinum Contributor

    I've done some more troubleshooting. First, I cleaned all the ground connections at the engine block, body, and battery terminal. I then used my meter to check the resistance of the ground under the dash to the battery and the reading would start around 100 ohms and roll up pretty quickly until it got around 1.5k ohms and then jump back down and do it again. I've never seen anything like that happen before. When I tested the wire from the temperature sender to the instrument cluster connector I got a very similar result. Thinking my cheap multimeter was giving erroneous readings, I pulled out my Fluke 179 and still got the same thing. I have no clue how to explain this phenomenon. Anyone have any clue why this is happening?

    So, I'm currently at a crossroads where I need to make a decision of whether to keep trying to chase this issue down and potentially tear into the factory wiring harness under the dash to figure out what's happening or join the club of old-school truck owners who have dead gauges and put an aftermarket gauge in.

    Any help, suggestions, and opinions are greatly appreciated.
  3. Conlan Rose

    Conlan Rose Active Member 2 Years 1000 Posts

    Is it possible that the gauge or the stepper motor in the gauge went bad and caused the gauge to peg. I don't know much about your gen of truck, but in the 90's trucks they had alot of small issues with stepper motors causing gauges to fail or read weird.
  4. Crawdaddy

    Crawdaddy Epic Member Staff Member 5+ Years 1000 Posts Platinum Contributor

    I spoke to a local gauge repair shop and he said the gauges in my generation don't generally fail, but that it could have. Next time I'm at the junkyard I'm going to hope I can find a replacement gauge to test the gauge. From what I've read though, I'm probably going to have to find a 1991 truck to get the gauge.

    - - - Updated - - -

    Does anyone have the theory/method by which these gauges work? If I can wrap my head around what terminal does what and how it works, I can build a quick test rig to test the gauge by itself outside of the truck.
  5. Crawdaddy

    Crawdaddy Epic Member Staff Member 5+ Years 1000 Posts Platinum Contributor

    I now have a resolution to my issue. Today I bought another instrument cluster from the junkyard and pulled the water temperature gauge from it and put it in my cluster. The gauge now appears to be working properly. I'd never have called the gauge going bad like that, but it did. I also noticed with the bad gauge that while the gauge was pegged when I turned the ignition on, it would still go a tiny bit higher when the truck got up to temp, so it was working in some minute way. But thankfully, my issue is now fixed.

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