I have 02 Trailblazer and it seems that with the AC on the temp rises to around 220.I think that's hot.I'm use to seeing it run around 210.As soon as I turn the AC off the temp returns to normal.The clutch fan has plenty of resistance when I turn it so I don't think its that's.Does anyone have suggestions?

 

I moved your post into a new thread in the GMT360/370 platform section which covers your 2002 Trailblazer (different from the 2002 s-series Blazer).

I would start by cleaning the exterior of the radiator. You can remove the fan shroud and spray water back through the radiator towards the front of the truck to clear debris from the radiator and condenser. You may have marginal cooling when the A/C is not on which is then insufficient for the heat generated in the condenser.

 

Thank-you for your help and moving my post for me

 

Check your coolant level too.

 

Provided the thermostat is not bad, it's going to be the radiator. I just went thru this with my 02 Trailblazer. It was overheating and the mechanic told me that the radiator could not possibly be clogged up. He was wrong, it's very stopped up. I replaced the radiator and now it runs 195 all the time and the needle never moves. Looking at the age of it and the coolant probably not serviced will lead to them clogging up. It's what happened to me.