York Furnace cycles too much

[jls667]

Brand and Model: York P3URB12N07501A - 4 burner

The outside temperature was about 0 degrees F the other day. My thermostat was set to 70 degrees F. The room temperature kept going from about 55 to 65 F and the red error light blinks 4 times. Even though the 4 lights mean a limit switch, I had an extra circuit board, so I tried that. Same problem. It seems like the duct gets very hot and trips the hot temperature switch. When I take off the cover, the burners only stay on between 3 and 4 minutes, even when the thermostat calls for more heat. All my vents are wide open. The blower motor seems to be working. Do I change the high temperature switch? Should I change the blower motor? Can I increase the speed of the blower motor? Any suggestions would be greatly appreciated.

John

[jls667]

I just want to add a few points. I checked the fan wiring on the circuit board. The important colors from the motor are black, blue, red and probably yellow. The first three I know are hi, med and low speed. The black is on the hi cool tab. The red is on the heat tab and the other two are on the park tabs. Can I swap the blue and the red to speed up airflow on heat?

[charlienamatjira]

I think there is problem with your temperature switch.You have mention that all your vents are open and still switch continues to show red alert light,it means it is getting hot internally,so there is problem in switch only.

[jls667]

I think there is problem with your temperature switch.You have mention that all your vents are open and still switch continues to show red alert light,it means it is getting hot internally,so there is problem in switch only.

I ended up speeding up my motor. I believe that the airflow was too low to keep the heat exchanger from overheating.

[jnaas2]

Is this a new install or has this unit been operating for a while, If its been running for a year or more and this problem is new then its something besides the fan speed. At install the furnance should of been checked for temperature rise and fan speed set accordingly