I have a trane xl 80 model tud080k93640 that today I saw that the thermostat was at 62 so I turned it up to 66 and nothing. I went down stairs and the 4 blinking lights told me thermal protection device open. I turned every thing off and restarted it. The burners kicked on and the exaust fan kicked on but the fan didn't kick on to blow heat up stairs. It ran for 3 min and turned off showing 4 blinking lights again. I have turned the fan moter on buy itself and it is running fine. I let it run for 10 min or so then switch the thermostat to heat and wait for it to turn on and it runs fine.

Sounds like a problem with the heating speed blower operation - could be the motor or the furnace control. Fault code is resulting from furnace overheating.

Furnace control like the thermostat?

I have noticed that the heat 2 on the thermostat has came on a lot often. We just put in a airconditioning unit could it be that its 10 yrs old and needs a new motor? How much does a motor or furnace control cost?

No, the circuit board that controls furnace operation. If the blower runs continuously with the thermostat fan selector set to "on", the circuit board is more likely the problem.

i have noticed that the heat 2 on the thermostat has came on alot often. We just put in a airconditioning unit could it be that its 10 yrs old and needs a new motor? how much does a motor or furnace control cost?The "heat 2" indicator displayed could be a result of the system not maintaining the space temperature within 1-2 degrees of the setpoint, and activating a second stage output.

Is the circuit board something I could replace myself? And how much if you know would one of these cost. Buy the way thank you so much for your help I am kind of a novice.