I have a 2000 Jimmy - 4wd. I also live in Chicago, and as you may all know, it tends to get a bit cold up here. Well, I bought my Jimmy in July and it has ran very well. However it is now November and getting as low as 25 degrees at night and I would love to have HEAT. It blows luke warm air when its been running for a while. The temp gauge almost NEVER gets above the quarter hash mark on the temp gauge - except when I was in bumper to bumper traffic downtown in August OR towing a trailer and even then it just barely got over that hash mark. Anyways, I can't tell if I'm looking at a new t-stat (maybe mine is just open and it needs to get warmer) or if the heater core is full of crud, or its something completely different. The only thing I have changed since I purchased it was the radiator and cap but that was because I had a leak. Any help would be much appreciated.

Thanks guys (and girls)!

Mike

 

Either your temp sensor is faulty or your thermostat is stuck open. Since you're not getting much heat I'd start by replacing the thermostat...a 10/10 job....10 minutes and 10 bucks.

 

I would agree, It sounds like your thermostat is stuck open.

 

I have no problem changing out the t-stat. But if that was the problem and it was "always open" wouldn't it take quite a while to even get to that 1/4 mark? In theory if it is stuck up the cold coolant would keep pumping into the motor and it shouldn't warm up quick at all. However it actually warms up to that mark relatively quickly and then sits there.

 

It depends on where the thermostat is stuck. If it's not fully open then it's possible that the motor can heat up quite quickly. It might be a situation where it's only moving between 1/2 open and fully open. If you take it out when the engine is cold it should be easy to see if it's open. There's not a lot of things that will cause an over cooling situation unlike an over heating condition which can have multiple causes...sometimes all at once.

 

Thanks everyone! Changed out the t-stat with a new one from Autozone for 8 bucks and sure enough it did the trick! Thanks a ton!