Temperature guage on 79 chevy g20 goes haywire, back and forth between hot and cold


Asked by Mar 02, 2017 at 05:38 PM about the 1979 Chevrolet Chevy Van

Question type: Maintenance & Repair

Have replaced the thermostat twice and guage keeps doing the same
craziness, back and forth. If I'm up to high speed on freeway, the guage levels
off on cool. Sometimes, as Im driving along a street, it'll level off to cool. Other
times, its a back and forth thing. If it idles, sometimes it's okay and not moving
and other times it's all over the place. What could be causing this?

4 Answers


Carefully inspect the wire(s) coming from the temperature gauge sending unit on the engine. Make sure there's no bare spots on the insulation. If the wire has a bare spot and intermittently touches metal it will cause the gauge to jump around. HTH. -Jim


Check head gaskets too.

1 people found this helpful.

Jim, do you know where the temp guage sending unit is on this engine?

1 people found this helpful.

Not off the top of my head. It's probably either at the thermostat housing or screwed into the side of one of the heads. It'll have at least 1 wire plugged onto it. HTH. -Jim

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