coolent temp gauge inop

[johnanc]

installed new engine and new coolent temp sensor, gauge doesn't indicate any temp.. used teflon tape on sender threads, someone suggested that sender not getting ground with tape in place- anyone have any info. would someone tell me if sender normally generates voltage which is what powers gauge? thanks, john

[Jeremy-WI]

The coolant temp sensor is a thermistor, the resistance changes rapidly due to temperature change, the sending unit for the dash definitely needs a good ground as it usually is a one wire unit. The guage itself it just a voltmeter set up to readout temp instead of volts. The changing resistance of the sending unit changes the voltage running through it

[quaddriver]

Originally Posted by johnanc

installed new engine and new coolent temp sensor, gauge doesn't indicate any temp.. used teflon tape on sender threads, someone suggested that sender not getting ground with tape in place- anyone have any info. would someone tell me if sender normally generates voltage which is what powers gauge? thanks, john

you dont say what year, what engine, but typically, the sensor for the gauge and the sensor for the ECM are two different entities. the ECT/CTS (it changed its name) is typically on the intake manifold and has two wires. if you want to see if it is working, hook up a scan tool, go into data or streaming mode and watch the temp as the ECM sees it.

the temp sender is typically on the side of the motor or in the head, but also on the side and has 1 wire. If you have a blazer with a 4.3, this is on the passenger side between plugs 2-4 but a little lower, if you have a big blazer with a 5/5.7 then it is on the drivers side near plugs 1-3

[sleslie17]

I have a 4.3L and it is on the drivers side near the plugs - I know because I mistakenly removed it and the coolant came out. I was measuring about 10V from the wire to ground(block) when the water was warm and engine on. To test it if you do not have a scan tool - remove it heat up some water and watch the resistance change. If I were to guess, there is a voltage divider - the 12V or so is supplied back at the gauge and as the resistance changes in the sensor the current to ground changes and is measured by the gauge.

-Shawn