i have been chasing this problom for almost a year, and i cant figure it out. the guage will read 220f when the engine is warm, but i have checked the enigne with other gauges and a raytec gun and the motor is between 135f-140f so i know the motor is not overheating. i have replaced the guage, sending unit, the sending wire, cleaned grounds and the guage still reads about 70 degrees higher than the engine really is? anyone have any ideas?

anyone have any ideas? this is driving me nuts.

are you using any kind of thread sealant on the sending unit? it may be interfering with the grounding of it....

yes i do have white permatex on the sending unit. very well could be the problom. i will have to go home to do a little testing tonight. any other posabiltys?

Any chance the sending unit and the gauge are not compatable?

both guage and sender are right from gaffrig

the sealant/ bad ground is the answer. that was good thinking wally.

take the sender out and extend the signal wire and ground to battery so that you can put it in some heated water of a known temp. If the gauge reads correct then you most likely do have a grounding issue.

On the other hand I have bought a gaffrig oil temp gauge and sender that were not compatible. (read high)

use a multimeter to test for a good ground from the sender body to the block, should be zero resistance. This is a good idea any time you change any sender btw, regardless of what thread sealant you use.

the guage at one time read correctly. then i sent my engine out for a rebuild and dyno tune and ever since i got it back from the engine builder it has read 70degrees hotter than norm.