1999 XJ Classic.. Heat feels like a cool spring breeze, sometimes a 75 degree breeze.. Then drops back to say 60 degree feeling. Thermostat changed it runs at the line before 210.

One day when my mom was in the hospital last week it got up to 210 as i was sitting in the car not able to stay in the emergency room. It got up to a glorious 210 and I had actual heat!!!

Turned it off for 10 minutes went back outside boom cold heat temperature isn't even showing 190.

Radiator Flushed... Anti Freeze appears normal in reservoirs heats back to being spring like.

WTF is happening?

 

Did you flush out your heater core? The two hoses that run to the firewall and into the cab? They are often full of gunk as the passages are small. If you did, did you flush it through both ways or just one? You could also still have air trapped in the system.

 

like boxburn stated... heater core... and verify that you have the correct thermostat installed. The wrong one may not allow it to open and flow correctly even though the engine is up to temp.... which can certainly lead to other issues. So make sure that's right.