Coleman air conditioner runs continuously and rarely shuts off, even when the set temperature is reached.

Safety: Turn OFF power before removing thermostat or control board covers.

• Check thermostat calibration: Compare thermostat reading to an accurate room thermometer. If off by several degrees, recalibrate or replace the thermostat.
• Thermostat location: Ensure it is not in a drafty area or near heat sources that skew readings.
• Inspect control board: Look for a stuck compressor relay on the Coleman board (contacts welded closed). Replace the board if the compressor runs even with no call for cooling.
• Check for air leaks: Inspect ductwork for leaks in attics or crawlspaces and seal as needed.
• Refrigerant check: If the unit cannot reach setpoint despite long run times, have a technician check refrigerant charge and system capacity.

Note: In very hot weather, long run times can be normal if the system is correctly sized.