Heat Pump Not Heating? Troubleshooting Guide

Start with the obvious. Is the thermostat set to heat mode and at least 3 degrees above the current room temperature? Many no-heat calls turn out to be a thermostat accidentally left in cool mode or set too low. Check the circuit breaker. Heat pumps run on dedicated 240-volt circuits. If the breaker tripped, reset it once. If it trips again immediately, do not reset it again. You have a short circuit that needs a professional. Check the air filter. A severely clogged filter restricts airflow and can trigger the system's safety switch, which shuts down the outdoor unit to prevent damage. Replace the filter and wait 30 minutes before turning the system back on. Check for ice or snow blocking the outdoor unit. Clear at least two feet of space around it. Pour warm water over the unit to melt any ice buildup. Never chip at ice with a sharp tool.

If the outdoor unit is running but there is no heat inside, the refrigerant may be low. This usually means there is a leak that needs professional repair. If the system frequently goes into defrost mode, which is normal in cold weather, you may see steam rising from the outdoor unit. This is just water vapor and not a problem. If the unit is stuck in defrost mode, the defrost sensor or control board may have failed. This requires a service call. If you hear a loud buzzing noise followed by the system shutting off, the compressor may be failing. This is a serious issue that typically means replacing the outdoor unit. If the indoor unit is blowing air but it is lukewarm, not hot, the auxiliary heat strips may have failed. These electric resistance coils kick in when the heat pump cannot keep up on its own, typically below 15 degrees outside. If they fail, the system will blow slightly warm air but will not heat the house adequately.

Call for service if the outdoor unit is making grinding or screeching noises, if the circuit breaker trips repeatedly, if ice builds up on the outdoor unit in temperatures above freezing, if the system runs constantly but the house does not warm up, or if you smell burning. These are not DIY fixes. A qualified HVAC technician can diagnose the issue, which is often a failed capacitor, a refrigerant leak, a bad reversing valve, or a failed defrost control board. Most repairs cost between $200 and $800. If your system is more than 12 years old and the repair costs more than half the price of a new unit, replacement is usually the better long-term decision.