Jeepee

my temp gauge does not currently work. it will just sit right at 100. but the fan comes on when it gets hot. is there a separate temp sensor for the fan? or is the gauge itself bad? jw before i go replacing stuff.

95Cherokee

The rear sensor on the back of the engine block goes to the gauge, the one at the thermostat housing controls the fan I think.

troy fritz

The one on top of the head at the very back controls the gauge.They are like $15 at parts store. Be careful takeing it out and installing the new one.They are hollow brass and break very easy.

kbad

"....late H.O. engines have a combination coolant temperature sensor that also feeds the gauge! ......RENIX vehicles use a SEPARATE sensor located on the back half of the head, driver side.

To test, use a high impedance volt-ohmmeter. Resistance should be less than 1000 ohms with a WARM engine (examples = 212* would be about 185 ohms, 160* would be about 450 ohms, 100* (not warm enough) would be 1,600 ohms).

What does it do? Adjusts the injector pulse widths (Colder coolant temperatures result in longer injector pulse widths and richer air-fuel mixtures). Compensates for fuel condensation in intake manifold. Controls engine warm-up idle speed. Increases ignition advance when engine is cold. Energizes the EGR valve solenoid to prevent flow of vacuum to the EGR valve.

....Basically - this sensor functions by providing a resistance-to-ground circuit that the computer (ECU) uses to determine how much fuel the engine requires. (The hotter the coolant - the lower the resistance.) The resistance of the sensor is read by the ECU which in turn adjusts the air/fuel ratio as close to 14.7:1 as possible. When a coolant temperature sensor fails (open circuit / no continuity) the high / infinite resisitance will cause the ECU to falsely read the max low temperature of -40 degrees F. The ECU then tells the injectors to enrichen the fuel mixture because it thinks the temp is really cold when it really isn't. A short to ground would cause a 'no-resistance' fault causing the ECU to think the coolant air temperature was extremely hot and lean out the fuel mix."

source.... http://www.lunghd.com/Tech_Articles/...iagnostics.htm

troy fritz

The 96 models have a seperate one on the rear of head on ds.We have 3 96s in my fam and they are all that way.

Jeepee

okay. thanks for all the into guys! ill try not to break the sensor taking it out.. i did read earlier that they break very easily.

kbad

don't remove the sensor until you check the resistance across it - it may not be the problem! hot coolant = low resistance, cold coolant = high resistance.

...if you do remove it, you can test it's operation by placing it in a dish of hot water and measuring the resistance across the connector....