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

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)