My Trane XV90 won't stop heating. The thermostat is a Ritetemp 6080. The unit heats up to the desired temp and then just keeps going. I shut everything down when this started last week, started it back up and it was fine for a few days... then, it's cockin' in here again.

It is a 2-stage heating unit with 1 stage AC.

I get a 4-red error on the unit (which says open temperature limit switch)

Anything I can do for this issue before I have to call a service repair guy?

Thanks...