Guys,

my temp guage is fluctuating wildly, from 120 to 210. Most of the time when the vehicle is moving it drops to btw 120-140. sitting at idle warmed up to full operating temperature it will move back up to the middle and as soon as i take off again it drops.

The other clue is that when it drops the idle speed increases a little. Sometimes it will move up and down at a light and i can see maybe a 100 rpm difference in idle speed.

I believe there are two possible culprits - a temp sensor or a temp sender, any idea which is most likely the one that's not working.

Thanks

Chris

 

i forgot to mention, it's a 00' cherokee

 

The one on the back wouldn't control any of the motor components, since its strictly for the gauge, but it would seem its that since the gauge is going nuts. I would replace the cheapest one first, which I think is the gauge sender. I think its about 15 bucks.

The one on the front tells the computer the temp of the coolant, so the electric fan can turn on. Could be this but your gauge wouldn't be reading like it is so thats why I rule it out.

Make sure your electric fan is turning on.

 

Have you had your cooling system serviced lately? We had a similar issue on another car when the cooling system wasn't full, so the sensor was finding hot and cool spots because the coolant level fluctuating.

 

haven't had the cooant system serviced too recently but i think the mechanic replaced a hose and some coolant maybe 6 months ago. i driven it probably 5k miles since then. Coolant seems to magically disapear from this vehicle. That's been happening for a while. I have read that could have something to do with my substandard oil pressure, but that's another whole problem. Or maybe it's all related. any more suggestions - i'm all ears.