I drive a 2000 Cherokee 4.0 and it's been running fine. It had 86K when I started driving it back in Jan. Today I noticed that the temp gauge, which has traditionally read just above 210 and held there steady, had dropped to around 160. I looked at it a couple of min later and it was back at 210. Later, as I drove, I kept a watch on the gauge and it continued to do the same thing. The gauge would bounce every 2 to 3 min between 160 and 210 and it would be an instant change, not a gradual move. It now has around 92K on it and I've been trying to baby it the best I can. It's summer and I'm running the a/c a lot.

I've read some of the posts here that are related to temp gauge, thermostat, sending unit and based on what I've read it seems to be a sending/sensor issue. I can't see a sticky thermostat causing the gauge to bounce between the temps so quickly. Any one?

 

I would say it was the sending unit. It should move a little when the stat opens but that seems dramatic.

 

I would tend to suspect the sender as well, inexpensive and easier than a thermostat change... thats where i would start.

 

Ok, I recently noticed that while driving in stop and go traffic, when the cooling fan is activated, the temp gauge moves to the "believable" temp which is just past straight up at 210 F. When the fan switches off, the temp gauge goes back to the 1/4 position, say around 160 F. Does that give anyone any more indication of what is the source of the bouncing temp gauge? Some have replied and say it's the sending unit. Any other different or confirming opinions?

Thanks.

Scott

 

If you are not going above 210 then why really worry about it.

I mean you can change out some components and stuff. Anytime I buy a used vehicle I change all fluids to include a coolant flush. I assume you did none of that. So for all you know the prior owner never did either. So I would start flushing your coolant, replace or clean up your temp sensor and get you a new thermostat in there.

 

Check the electrical connector/connection on the sending unit at the t-stat housing. No way that puppy's going to run 160 this time of year, unless you live at the South pole. LOL