When I was trying to isolate an issue with my temp. gage, someone told me; to check the gage, attach your sensor wire to a good ground and your inside gage should peg to max. reading. I did not try it, so I can't say if it is true or not, but the one thought that came to mind is, if there is some truth to it, could your sensor wire be going to ground somewhere resulting your gage to read max. Just a thought. . . .By the way, my problem was opposite yours, gage would read, but would not read much over 100, turned out to be the sensor. . . .