84 4x4 SR5 temp gauge problem

1984 TOYOTA PICKUP
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MY84SR5
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The truck is a 1984 SR5, 4 x 4 truck with a 22R engine. My temperature gauge will sometimes work and sometimes not. It will move up into reading the temperature then suddenly drop like the engines off then go up then drop. It's gotten worse and worse over time. Now it will hardly read, just stays down. One mechanic checked and said I need a new gauge. Do I have to replace the whole instrument cluster?
Oct 8, 2007 at 3:09 PM
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MERLIN2021
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Before we take such a drastic step, lets try the temp sending switch!


https://www.2carpros.com/forum/automotive_pictures/62217_CTSU_1.jpg

It's in the coolant flange, on the right side of the block!
Oct 8, 2007 at 3:56 PM
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LJSTOY
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yep. the temp sending unit is on the pass. side on the intake by the thermostat. 84 didn't have very complicated wiring so i would follow the wire as far as possible to check for any loose connections. I went ahead and got an aftermarket gauge because i didn't trust the (it's either hot or it's cold) factory gauge. i wanted to know how hot is hot after rebuilding one motor already.
Oct 11, 2007 at 12:22 PM
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MY84SR5
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I had a new sending unit installed and the gauge worked fine for about 1 mile then went into the flipping mode again. The mechanic said the old sending unit had a short. He said if it still has the same problem it's the gauge. If it's the wire that's a problem because it's taped into a bundle with other wires.
Oct 15, 2007 at 12:59 PM