Heat Pump Not Heating? Troubleshooting for Vermont Homeowners
May 10, 2026
If your heat pump is not heating, the cause is almost always one of five things: a frozen outdoor coil, a tripped breaker, a clogged filter, low refrigerant, or a stuck reversing valve. The first three you can diagnose and fix yourself in 10 minutes. The last two require a tech.
Do not run the system for long periods if it is not heating. Running a heat pump without refrigerant or with a stuck reversing valve damages the compressor.
What to check yourself, in order
1. The breaker. Walk to your electrical panel. Look for a breaker labeled "heat pump" or "outdoor unit" in the tripped (middle) position. Reset it firmly to OFF then to ON. If it trips again immediately, stop. That is an electrical short or a failing compressor; call a tech.
2. The outdoor disconnect. A small gray box mounted on the wall next to your outdoor unit. Open it. There is usually a fuse pull or a small switch. Confirm it is engaged.
3. The filter. Open the indoor unit, slide out the filter, hold it up to a light. If you cannot see light through it, that is your problem. Wash it in warm soapy water, dry fully, reinstall.
4. Snow and ice around the outdoor unit. Clear at least 18 inches of clearance on all sides. Brush ice gently. Do not chip with a sharp tool.
5. The thermostat or remote. Replace the batteries. Make sure the system is set to HEAT, not FAN or AUTO. Set the temperature 3-5 degrees above the current room temp.
If any of these solves it, you are done.
What needs a tech
Frozen outdoor coil that does not clear within 45 minutes. Normal defrost cycles clear ice in 10-15 minutes. Persistent ice means a defrost sensor failure, defrost board issue, or low refrigerant. All require diagnostic work.
Low refrigerant. Symptoms: outdoor unit runs but the air coming inside is barely warm; ice forms on the refrigerant lines near the outdoor unit; bill is rising. There is no DIY for refrigerant. EPA 608 certification is required to handle refrigerant legally.
Stuck reversing valve. The valve that switches between heat and cool modes. Symptoms: system blows cold air in heat mode for more than 30 minutes, no defrost cycle pattern. Sometimes power-cycling the unit at the breaker for 10 minutes resolves it. If it persists, you need a tech.
Vermont-specific causes
A few things we see specifically in Vermont:
- Buried outdoor units after a snowstorm. Snow piled against the unit blocks airflow. Clear and elevate if you can.
- Frozen condensate drain lines. Especially in homes with the drain line running outside through an unheated wall cavity. The line freezes, condensate backs up, and the system trips.
- Wood stove smoke clogging the outdoor coil faster than typical. If you burn wood, the outdoor coil needs cleaning twice a year, not once.
When to call us instead of trying more
If you have done the five DIY checks and the system still is not heating, book a diagnostic visit. $129 flat, applied to any repair you proceed with. Same-week scheduling.
Symptoms that should skip DIY entirely:
- Outdoor unit is completely encased in ice
- The breaker trips immediately on reset
- Burning smell from the indoor or outdoor unit
- Loud grinding or screeching sounds
Book a diagnostic
Book in 60 seconds or call (802) 555-0100.