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  1. #1

    Default 1993 GMC Pickup - Factory Water Temp Gauge Died - Need Diagnostic Instructions

    The factory water temp gauge has died on my 1993 GMC pickup (4.3L V-6 engine). I believe that the trouble has to be in one of three places, ie: the gauge, the wiring, or the sending unit that is mounted in the block between the cylinders on the drivers side. I suppose the problem could even be a combination of any of those. I need the step-by-step instructions to diagnose exactly where the point of failure is. Thank you.
    -- My other truck was a Freightliner --

  2. #2
    Jr. Mechanic
    Join Date
    Sep 2007
    Los Angeles, CA


    The most likely culprit is the sending unit, the least likely your wiring. Do you have an ohmmeter? If you do, you can measure resistance across your sending unit at various temperatures. Resistance will change with heat. Fast way to diagnose you gauge: unplug your sending unit, and jump across the connectors on your wiring harness, the gauge should move over to hot. If it doesn't move, then it's bad. Check your wiring to make sure the insulation is not burned by the exhaust.
    Hope this helps.
    '88 Jimmy 4X4
    5.3l L59/ 4L60E Tuned by Tad
    4" Lift 33" BFG. Custom Brush Guard, KCs, outside spare, Oil pan guard etc.

  3. #3


    Thank you, Toymyster. Since I posted this thread, I have been doing a lot of online research into my dilemma. Basically, I have found what you advised me to do. I do not have, nor know how to use, a multimeter -- but there's no time better to learn than the present. I may not need one though if the problem lies in the sending unit or the gauge, because those two items can be diagnosed with a simple jumper wire according to what I have read online. But, there again, I am not sure exactly where to connect the jumper wire ends. For example: to test the sending unit I think that the negative post on the battery would suffice as a negative ground. But, should the other end of the jumper wire be connected to the sending unit or to the wire that runs between the gauge and the sending unit -- if the wire, then should the wire be disconnected from the sending unit or should it be connected, in order to run this test? I wish I had a good working knowledge of electrical systems, but unfortunately I do not -- thus I need a lot of guidance from those who do. Here are the links to the websites I found that have the test procedures for diagnosing a non-working temp gauge. I think the E-How instructions are better than the autozone, but, as you see, I still need help.

    Again, thanks so much for your help. I appreciate it, Toymyster.

  4. #4
    Jr. Mechanic
    Join Date
    Sep 2007
    Los Angeles, CA


    Think nothing of it. And a nice DMM is worth it's wait in gold. most of the good ones come with tutorials these days. Don't let them intimidate you.

  5. #5


    Toymyster, yes, I am sure they are IF one has a need for one. But, I am pretty sure I will not need one for this current vehicle problem, and I cannot afford to buy something just to have it laying around just in case I MIGHT need it at some future time. And if I ever did need to buy one, I would be financially limited to one in the $25 range at most. Actually, just out of curiosity, I was looking at them online the other day, and I found these 3 that seem pretty good for the money.

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