Heat Pump Running But Not Heating Is the air blowing out of the top of the unit noticeably cooler than the surrounding air? (a 9°F to 12°F difference is typical) If not, call AquaCal for service at 727-823-5642. Be sure all air coil surfaces are free from obstructions; low roof overhangs, landscaping, walls, fences, etc. The heat pump needs good airflow to operate at peak efficiency. How long are you running your circulation pump each day? Cooler weather conditions, or heating to a higher temperature, may necessitate running the heat pump for a longer period of time. A pool blanket can be useful in permitting shorter run times, in turn leading to substantial energy cost savings. What is the air temperature? Your heat pump may be in the defrost mode if air temperatures are below 50°F. The digital display will read “FS” if the unit is defrosting or air temperatures are too cold. >> Water Leaking Out Of The Heat Pump l Troubleshooting Guide