trouble shooting
COMBITHERM® CT PROFORMANCE™ SERIES • STEP-BY-STEP PROCEDURES • MN-35948 • 59.
ERROR CODES
Error 
Code
Error Call Out in Display Description of Error Possible Cause
E108
Cooling Fan Failure If the temperature on the 
control board (relay board) is 
greater than 140ºF (60ºC) and 
less than 176ºF (80ºC). (See 
error code E02)
— Cooling fan damaged.
—  Cooling fan blocked or blades have been kept 
from rotating.
— Incoming air temperature exceeds 100°F (38°C).
— Air inlet has become blocked.
E109
High Limit Switch The High Limit Switch input 
to the CB (N7) is “open”
— Unit has experienced an over heat condition.
— Convection element contactors stuck closed.
— Failed Y1 solenoid.
—  Obstruction between Y1 solenoid and injection 
pipe.
— Improperly connected drain.
— Condensate pan clean out not closed.
—  Improperly wired high limit switch at the switch 
or at the CB.
— Defective high limit switch.
see motor control error chart on next page