Q: Temperature gauge moves up and down rapidly (does'nt jump).

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when I bought this van the temp gauge did not work at all after tests the gauge was declared good the coolant sensor was replaced and tested ok. after looking at a wireing diagram I saw that a rd/wt wire went from the sensor to the gauge with a yl/lb branching off to the pcm I ran a trial wire from the sensor to the yl/lb right at the pcm now the gauge moves up and down and the high temp light comes on and goes off depending on the engine rpm

van has 220000 miles runs great
My van has an automatic transmission. (rebuilt)

The wire yl/lb from the PCM to the coolant temperature sensor seems to have a break in it. However, when jumping the wire from the PCM to the sensor could have been in contact with another circuit causing the gauge to bounce. Try taking an alligator clip jumper wire and hooking it to the wire directly next to the PCM and right next to the sensor and then cut the yl/lb wire to break the circuit. If the gauge works fine, then the yl/lb wire needs replaced. If there is no change, then either the ground circuit on the gauge is shorted out with the tachometer gauge or the gauge is not working properly. If you need further assistance with your gauges, then seek out a professional, such as one from Your Mechanic, to help you.

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