A tale of two temp gauges

96 Sport

Recently replaced everything related to the coolant system with the exception of the heater core. All water was clear after a flush. I upgraded to a 2 row CSF radiator and ZJ fan clutch. The factory gauge was reading high (I've only had the truck since February) so I decided to replace most of the components and it didn't change the high readings.



I installed an electrical gauge off of a t fitting on the thermostat housing. The readings between the two are about 50 degrees apart. Example: The aftermarket gauge reads 200 and the factory gauge reads 250. Any ideas? I'm hoping the factory gauge and/ or sending unit are faulty.

Your 96 is OBDII, and uses the coolant sensor in the thermostat housing to drive the gauge. Its probably defective, lots of them are junk. You can validate the gauge with the sensor with an OBDII scanner that shows temperature data; if they are the same then the gauge is accurate for the sensor. You can use an IR temperature gun on the housing to establish another data point to see if the sensor is defective.

On a 96 the gauge is run by the temp sender in the back of the head.
The temp sensor in the T-stat housing is for the ecu(computer)
On 97+ the temp sensor supply,s both the ecu and the(thru the ecu)gauge.
On my 96 there is a 15* difference in the temps-checked by a scan tool-Snap-on and the aftermarket(autometer)sender in the back of the head.

Temp sensor inhousing-195*,,,,,sender in back of head 215*.

Thanks for the replies. Yeah, I have the sending unit for the gauge on the back of the block. I'll hook up my scan gauge this afternoon and see what I get.


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I'd be inclined to trust the aftermarket gauge, especially if its an autometer, but a defective sending unit is always possible...

Validate with a laser IR Thermometer on the t/stat housing, I wouldnt trust a second 20 year old sending unit to validate that the sky is blue...

Sorry 96 is transition year it gets me everytime

So the scanner reads well below the factory gauge but 10 above the glow shift gauge. At least I confirmed that I don't have an overheating issue. Thanks again for the replies!


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sender is defective, buy Mopar or Standard brand, hope for a good one, try again if you don't