Heat pump won’t shut off: causes, part cost
Prices checked 2026-08-28
A heat pump won't shut off is most often a faulty thermostat or switch problem - about 34% of reported jobs. Here is how to confirm it, what the part costs, and when to stop.
A heat pump is an air conditioner that runs both ways, which means twice the switching hardware and one more set of things to fail – but the fault logic is the same airflow-versus-refrigerant split.
Heat pump won't shut off is one of the most common repair searches there is. A unit that will not shut off is stuck on – a switch, thermostat or relay is holding the circuit closed, or the unit is working harder than it should to reach its target.
Before you call anyone: 30-second checks
- Check the thermostat or sensor reading – a stuck-open thermostat makes the unit run forever.
- Check the switch and controls for a stuck position.
- Check for a constant demand – a leaking flapper, a bypass valve or an open door keeps systems running.
The likely causes, ranked
Faulty thermostat or switch
About 34% of heat pump won't shut off jobs come back to this cause. Switches and interlocks tell the unit it is safe to run, and a stuck or failed switch can stop a unit dead or leave it running when it should not.
How to confirm it: A unit that will not start, or starts only when the door is held, points at the interlock switch – a cheap, common part.
Typical fix: $60. A capable DIYer can usually handle this one. You would be looking for a thermostat.
Control board relay stuck
About 26% of heat pump won't shut off jobs come back to this cause. A motor, fan or pump with its drive components is a wear item – belts stretch, bearings dry out, capacitors lose their charge and relays stick.
How to confirm it: Listen for the motor: a hum with no movement points at a capacitor or belt; a grinding or squeal points at a bearing. Each has a different price tag.
Typical fix: $180. This one is best left to a professional. You would be looking for a control board.
Stuck relay on the timer or selector
About 22% of heat pump won't shut off jobs come back to this cause. A motor, fan or pump with its drive components is a wear item – belts stretch, bearings dry out, capacitors lose their charge and relays stick.
How to confirm it: Listen for the motor: a hum with no movement points at a capacitor or belt; a grinding or squeal points at a bearing. Each has a different price tag.
Typical fix: $90. This one is best left to a professional. You would be looking for a timer.
Leak or bypass causing constant demand
About 18% of heat pump won't shut off jobs come back to this cause. This is a component-level failure – the part itself has worn out or failed, which is why it sits on the ranked list rather than the free-check list.
How to confirm it: It is worth confirming with a multimeter or a visual check before ordering the part, and worth asking the shop if the part is returnable.
Typical fix: usually free. A capable DIYer can usually handle this one.
When to stop and call a pro
If the unit runs with the control off, the relay or switch is stuck closed – that is an electrical fault and worth a trade visit before it damages the motor.
How to keep it from coming back
Most run-forever faults are a sensor or switch that drifted. Replacing a $20 thermostat beats paying for the extra energy it consumes every month it runs.
Bottom line: Heat pump won't shut off is worth diagnosing before you call anyone – the free checks above catch a surprising share of cases, and the ranked list tells you what the part should cost if it is not one of them. Run the figures through the repair-or-replace test on this page before you authorise any work, and never pay for a diagnosis without getting the part name and the price in writing first.
Likely causes, most common first
| Likely cause | How often | Typical fix | Who does it |
|---|---|---|---|
| Dirty filter or coilsair filter | 30% | free | DIY-able |
| Low refrigerant / leakrefrigerant charge | 28% | $400 | Pro job |
| Faulty reversing valvereversing valve | 24% | $350 | Pro job |
| Failing compressor contactorcontactor | 18% | $90 | Pro job |
Frequencies are the share of reported jobs attributed to each cause across repair-platform and forum data - a starting point for diagnosis, not a certainty.
What this should cost to put right
Across the causes listed above the repair runs $0 to $180. A quote far above the top of that range is usually a diagnosis of convenience - get a second opinion before you authorise it.
Repair it, or replace the unit?
This is the number people get wrong most often, and it costs them the most. Run the quote through the test - it uses the mid-point cost of the fix above against a new unit and the years this one has left.
REPAIR IT
The repair is 10% of a new unit and the appliance has roughly 6 year(s) of expected life left. Fixing it is the economical call. A new unit would save about $45/year in running costs, so keep repairing until that pays back in under 5 years.
Decision rule: repair when the fix costs under 50% of a replacement and the unit is under 70% through its expected life.
Other heat pump symptoms
Common questions
Is it dangerous if my heat pump has a "won't shut off" problem?
Usually not immediately - none of the likely causes on this page involve gas, fuel or a mains electrical fault. The two cautions that apply everywhere: keep water away from any electrical point, and if you ever smell gas or burning, stop diagnosing and call a professional.
How much does it cost to fix a heat pump with a "won't shut off" problem?
Most fixes for this run $0 to $180. The most common cause, faulty thermostat or switch, runs about $60 to put right, and the part you would be looking for is thermostat. Get the diagnosis in writing before authorising anything above the top of the range.
Why does my heat pump have a "won't shut off" problem?
In about 34% of reported cases it is a faulty thermostat or switch. It is the first thing to check because it is the most common - and usually the cheapest. If that checks out clean, work down the ranked list on this page before paying for a diagnosis.
Should I repair or replace my heat pump?
Repair it when the fix costs under half of a replacement and the unit is under 35% through its roughly 15-year expected life. Past that point a repair is usually a deposit on the next failure - run the test on this page with your actual quote before you decide.
How this figure was built
Reviewed 2026-08-28 · quarterly.
- Bureau of Labor Statistics, Occupational Employment and Wage Statistics - construction and repair trades
- EPA Energy Guide appliance ratings
- North American Electrical Metrics / manufacturer parts catalogues
National averages. Local labour can run 20-40% above or below these figures; the calculators apply a metro factor on top.
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