[TR] TR6 temp gage issues

[dave n]

after the car sat for several months while doing transmission work, the temp
gage now pins right as soon as the car fully warms up.  radiator is relatively
cool, not steaming out or anything.  Ibm pretty sure the car is not
overheating, and it did work fine some months ago.  Ibve opened up the
thermostat cover and it all looks good.

I replaced the temp sensor with an older one I had around, and as far as I
know is working, same result.  tested it with hot water; get about 100%
connectivity using my tester when cold; drops way off when hot.

take the original sensor, hook it up to another gage which I think works,
using hot water, spare voltage regulator, and it seems to work fine.

different used gage I had around, same result.

hook up the used gages, voltage regulator, wire it up battery to vr (grounded)
to gage to sensor in car, it pins right when the car is warmed up.  same for
other gage.

I could use some advice on what to do next.