Hey, guys, so I have had my 55 GMC for a few years now and really enjoy it, I do not drive it that far, but it is a lot of fun to just go short distances around town. To make a long story short, the wife and I have been toying with the idea of taking this truck on some longer trips around Southern California. I have no doubt the truck can handle it no problem but my main concern is since day 1 the temp gauge never worked, and after many attempts at trouble shooting the problem I have yet to get it to work. So to sum up what I have already done to try and get it working, I have replaced the sender, the gauge, the wiring between the gauge and the sender, and still no luck. According to the manual the gauge gets 12 volts to the gauge housing then stepped down in voltage with a 30 ohm resister and then fed into the gauge. Then the other pole from the gauge goes to the temp sensor and thats it. As wired up the gauge moves all the way to cold. if I jiggle the gauge about and get the needle pointing towards hot, once you give power to the gauge it goes cold. Which is great except for it never moves from there. No matter how hot the engine gets the temp gauge stays right at cold and never moves. I have replaced all the wiring involved, I have a spare gauge that was working in another truck to troubleshoot with, and I have now replaced the sender twice. According to the manual, the first set of tests is to test the voltage from the positive of the battery to the sender housing, that should read 12, and then if I read the voltage to the center of the sender then it should read 0, but it doesnt, it always reads 12, even though when tested for continuity between the sender and the sender housing I get nothing. So I guess what I am trying to find out is what bozo mistake am I making, the thing I am most not sure about is if the sender needs to be NTC or not but that is the sender I keep buying, I cannot seem to find a PTC sender in the correct size. Any help is appreciated
If you can find a 500 ohm linear variable resistor a 9volt battery (Transistor radio type) Connect the battery to the gauge and its ground connect the center terminal of the resistor to the sending unit terminal and one of the other terminals to gauge ground. as you turn the resistor the gauge will climb from cold to hot. Use an ohm meter and measure (disconnect the gauge when measuring the resistor) the resister. Say it reads 300 ohms hot(full scale) Now put your sending unit in a pan of water heat water and watch resistance rise . read resistance. it should be 300 Ohms. (or whatever your resistor read at full scale). If you have any questions PM me. Terry aka dirt t
what sender is it? where did you get it? does it have a part number? what is the resistance cold and hot? I've had some trouble with the early Chevy electric temp gauges having an intermittent connection inside, so they read dead cold unless you wiggle the wire just so.
I tried setting up a bench test like dirt t had suggested and got some reallly weird readings on a volt meter and stranger readings on the gauge itself, pretty sure the issue might ultimstly be the gauge, as i would wiggle the gauge it goes really crazy, so i looked up on ebay for a replacement and found a nos mechanical gauge and picked that up for 100 bucks, figured that was easier than figuring this electric shit out... The sender brand is bwd, wt203p is the part number, but for the life of me i couldnt find a data sheet to find out the specifics to dial it in.
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