Temp gauge mystery

My first thought is the IVR is malfunctioning.

Does your fuel gauge do the same?



IVR function...

At first power on the IVR heating element starts to heat up. This takes a few seconds so full 12v is supplied to the temp and fuel gauge.

That has the effect of heating the gauge heater up faster.

Once the IVR reaches normal operating temp it then starts to open and close, pulsing the 12v to result in about 5 to 6v that the gauges need.

Now in your case the gauge will sweep fast to high then settle back to low.

This is not normal

Testing.

Turn the key to run, then short the temp sender wire at the temp sender to ground for a VERY short amount of time. Like 1 to 2 seconds. Have someone watch the gauge, it should rapidly sweep to high. If it does then the gauge and IVR might be good

DO NOT LEAVE IT SHORTED FOR MORE THAN ENOUGH TIME TO SEE THE NEEDLE MOVE.

if you do you WILL burn out your gauges