Volvo: overheat indication, checker auto store, voltage stabilizer

Question
QUESTION: My 1980 240 recently started indicating full hot on the temp gage. I replaced the radiator a couple of weeks prior for a leak and since have replaced the sending,unit water pump,and thermostat with no help....It started right after i selected full hot with the heater control???? Would a problem with the heater core cause this???

ANSWER: Richard,
Can't see how using the heater would cause the gauge to pin. Is the car really getting hot or is gauge just read hot? Measure the temp at the t/stat housing, should not be over 200*F. Maybe the voltage stabilizer has shorted out. It is on the rear of the cluster. That controls voltage to the gauges.

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QUESTION: I thought about the voltage stabilizer, but if it was shorted would it not affect the fuel gage also? Also i tried shorting the gage wire to grd. and the gage needle rises like the manual says it should.......Do you know of an after market gage i could install to elimnate the gage being the problem?

Answer
Richard,
Last gauge I got was from a Checker Auto store and it did have some fittings that came with it. Are you sure that the fuel gauge is reading correctly? My experience has been the fuel gauge reads, but not correctly. It may read higher or lower, not pinning itself.