Unusual overheating

[Adam]

So your car starts overheating, you've checked the usual, coolant, radiator, thermostat, pump, hoses... well it may not be your cooling system at all, check if changing the electrical load (eg. turning your headlights from off to high beam) changes the temp reading... if so, somewhere you will have a bad connection, possibly the earth to the guage itself, or in a million other place... but at least now you know what to look for, eh?

[rodeo bob]

i had a hq one tonner years ago and to check the temp and oil guages at night u had to turn the head lights off to get a true reading. it had a real touchy temp guage u could see it move when the thermostat opened. the guage used to go up and down when the indicators flashed. it was all bad earth.