allright guys I just bought a 1999 cherokee about 4 days ago and today the temp gauge won't respond.....at first it was a little above the middle then it would randomly drop down and come back up....today it isn't doing squat...... so where is the sensor and what is the easiest way to fix this gremlin?

 

In the t-stat housing. Problem could be bad wire connection, the sensor, maybe both.

 

Mine has been bouncing around, I unhooked it and cleaned the pins. Seems to be better so far.
That talks to the ecu too, and makes it run rich when it reads "cold" (I could hear my idle change) so its a good idea to change it/get it working right.

 

hey man .... ditto Defiance and DJB .... on 97+, the temp sensor (feeds ecu) and temp sender (feeds gauge) are all-in-one ... pull it and test it with a high impedance ohm meter .... resistance should be less than 1K ohms with a warm engine (212 deg is about 185 ohms, 160 deg about 450 ohms, 100 deg about 1.6K ohms) - you can use hot water to see the change on the bench .... good luck!

 

I cleaned the connections and it seems to popped back on. I will replace it in the long run. My only other project has been a 73 bug so working around radiators is a new thing to me.....which leads to my next question.....if the car is parked and running at what temp should the fan off to the side kick on?

 

I am new to the jeep fan set up my self (clutch fan + electric fan) It seems that if your clutch fan is working correctly the electric fan may not kick on when you would expect it too.The temp I think is 212deg and above. I could be way off on that, I'm sure somebody will let me know

 

thanks for the help and leads I will check to see if the fan is on when I drive home from work.

 

Efan kicks in at 218F coolant temp or when a/c compressor engages on '99 and earlier. I can't imagine coolant temp activating the efan this time of year with a good fan clutch on the belt driven fan and the rest of the cooling system functioning properly. O2 sensor(s) do way more at controlling rich/lean than coolant temp sensor, especially on OBD-II systems.....O2(s) take over with-in seconds of engine start-up.