Heat Pump Not Heating? What It Means and What to Check
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In San Jose and the South Bay, a heat pump that isn’t heating is most often set wrong, starved of airflow by a dirty filter, or iced over and stuck in defrost; less often it’s low on refrigerant from a leak or has a failed part such as the reversing valve or outdoor fan.
Start with the thermostat, the filter and the outdoor unit, which are safe for anyone to check. Anything electrical or involving refrigerant is a job for a licensed HVAC technician, and CPI Service can usually diagnose it in one visit.
Is Your Heat Pump Actually Broken?
Some things that feel like a problem are normal for a heat pump, especially if you’re used to a gas furnace:
- The air feels warm, not hot. A heat pump moves heat in from outside rather than burning fuel, so the air at the vents is milder than furnace air and the system runs longer, gentler cycles. ENERGY STAR notes that a heat pump can deliver up to three times more heat energy than the electricity it uses.
- Frost and steam outside. On cold, damp mornings, frost builds on the outdoor coil. The heat pump runs a defrost cycle to melt it, and you may see steam rising from the unit and feel cooler air indoors for a few minutes. Lennox calls light frost normal.
- It runs for a long time. Long run times on cold mornings are how heat pumps work. The problem is a house that never reaches the setting.
- A big setback takes a while to recover. ENERGY STAR advises keeping a heat pump at a steady temperature rather than setting it back, and using Heat rather than Auto so the system doesn’t switch modes on its own.
If the heat at the vents is cool rather than mild, see why your HVAC isn’t blowing warm air, which covers that symptom in detail.
Heat Pump Not Heating: What the Symptom Tells You
| What you see | Likely causes | Safe check | Call a technician when |
|---|---|---|---|
| Nothing runs, indoors or out | Thermostat off or dead batteries, tripped breaker, outdoor disconnect off, failed control | Thermostat mode and batteries; reset a tripped breaker once | The breaker trips again, or nothing starts |
| Indoor fan runs, outdoor unit doesn’t | Failed capacitor or contactor, outdoor fan or compressor fault, control problem | Outdoor disconnect and breaker on | Always: the parts are high voltage |
| Outdoor unit runs, air is cool | Defrost cycle, stuck reversing valve, low refrigerant | Let a defrost cycle finish; check that the thermostat says Heat | It doesn’t warm up after defrost |
| Outdoor unit covered in ice | Defrost control or sensor failure, low refrigerant, blocked airflow, failed outdoor fan | Turn the system off, clear around the unit, check the filter, let it thaw | Ice returns or stays for hours |
| Runs nonstop, house won’t warm up | Dirty filter, closed vents, leaky ducts, refrigerant leak, undersized system | Filter, vents, doors and windows | Still short of the setting with a clean filter |
| “Aux” or “Em heat” on most of the time | Heat pump not keeping up, failed outdoor unit, thermostat set-up | Thermostat set to Heat, not Emergency Heat | It stays on aux for hours; bills jump |
| Turns on and off every few minutes | Oversized system, dirty filter, thermostat location, refrigerant or control problem | Filter; thermostat away from heat sources | It keeps short cycling |
| Grinding, screeching or loud buzzing | Fan motor bearings, loose parts, failing capacitor or contactor, compressor | Turn it off | Right away, before it causes more damage |
Causes are from Lennox’s frozen heat pump guide, ENERGY STAR and the repairs on CPI’s heat pump service page. Checked October 2026.
What Can You Safely Check Yourself?
1. The Thermostat
Make sure it’s set to Heat, not Cool, Auto or Fan, and the setting is a few degrees above room temperature. Replace the batteries if the display is faint or blank. If you have a new smart thermostat, check that it’s set up for a heat pump; a thermostat configured for a furnace may call the wrong mode.
2. The Air Filter
A clogged filter cuts airflow, makes the house slow to warm and can help the outdoor coil ice over. ENERGY STAR suggests inspecting the filter once a month and cleaning or replacing it when it’s dirty. On a ductless system, rinse the filters in each indoor head.
3. The Vents and Registers
Open supply vents in every room and keep return grilles clear of furniture and rugs. Closed or blocked vents cut the airflow a heat pump needs to heat the house.
4. The Outdoor Unit
Lennox recommends keeping at least two feet clear around the outdoor unit. Rake away leaves, move stored items, trim plants, and make sure gutters and downspouts don’t drip onto it.
5. The Breaker
If nothing runs, check the breakers for the indoor unit and the outdoor unit. Turn the thermostat off first, then reset a tripped breaker once. If it trips again, leave it off and call: a breaker that keeps tripping is protecting you from an electrical fault. See why AC and heat pump breakers trip.
6. An Iced-Over Unit
If the outdoor unit is encased in ice, Lennox’s advice is to turn the system off at the thermostat (or use emergency heat to stay warm while it thaws), clear the area around it and check the filter. It says natural thawing usually takes two to four hours when it’s above freezing, and to call a technician if ice is still there after six to eight hours or comes back quickly. Don’t pour hot water on it or chip at the ice: both can crack parts or damage the coil fins and fan.
What Should You Leave to a Technician?
Anything Electrical
Heat pumps run on 240 volts, and the outdoor unit and air handler contain capacitors that store a dangerous charge even with the power off. Don’t remove access panels, touch wiring, swap capacitors or contactors, or jump controls. Turning the system off at the thermostat and resetting a breaker once is as far as a homeowner should go.
Anything Involving Refrigerant
A heat pump that’s low on refrigerant has a leak; refrigerant isn’t used up. Under EPA Section 608, technicians who maintain, service or repair equipment that could release refrigerant must be certified, and intentionally venting refrigerant is prohibited. Adding refrigerant without finding the leak only delays the next breakdown, and the wrong charge damages the compressor.
Parts a Technician Tests
- Reversing valve: switches the heat pump between heating and cooling; if it sticks, you get cooling in heat mode.
- Defrost control and sensors: start and end the defrost cycle; when they fail, ice keeps building.
- Outdoor fan motor and capacitor: without the fan, the outdoor coil can’t pick up heat from the air.
- Backup heat strips: cover defrost and cold mornings; a failure shows up as cold air during defrost.
- Compressor: the heart of the system, and the most expensive repair.
- Ducts: leaky or crushed ducts lose heat to the attic or crawl space before it reaches the rooms. See duct repair.
Heat Pump Problems in San Jose Homes
- Mild winters, damp mornings. San Jose’s winters are mild, which suits heat pumps, but cool, damp mornings are exactly when frost forms on the outdoor coil. A working defrost cycle clears it; a unit that stays white needs a technician.
- Leaves and side yards. Outdoor units here often sit in narrow side yards and under trees, where leaves and stored items block airflow.
- Converted furnace homes. Some South Bay homes have switched from a gas furnace to a heat pump. If yours feels cooler than the old furnace but reaches the setting, that’s normal; if it never reaches the setting, sizing and ducts need a look.
- Rebates if you replace. As of October 2026, the main local rebates are for heat pumps that replace gas heating, such as San José Clean Energy’s EcoHome Rebate of $1,500 ($2,500 income-qualified) for heat pump HVAC replacing a gas furnace. See SJCE EcoHome rebates and rebates by city for the conditions; some programs need approval before installation.
When Should You Call an HVAC Technician?
Call a licensed technician when:
- the heat pump won’t start, or the breaker trips again after one reset
- ice stays on the outdoor unit for hours or comes right back
- the house won’t reach the setting even with a clean filter and open vents
- the system runs on auxiliary or emergency heat most of the time
- the outdoor fan doesn’t spin while the unit runs, or you hear grinding, screeching or loud buzzing
- you see oily residue on refrigerant lines or hear hissing, both signs of a refrigerant leak
CPI Service is licensed (CSLB License #1101278, including C-20 HVAC), offers same-day service and 24/7 emergency service, and backs its work with a 1-year labor warranty.
What Does Heat Pump Repair Cost in San Jose?
Typical CPI prices in San Jose, as of October 2026. Many heat pump repairs use the same outdoor-unit parts as an air conditioner:
| Repair | Typical cost in San Jose |
|---|---|
| Diagnostic visit (inspection fee) | $59, waived for service plan members |
| Thermostat replacement, installed | $200–$500 |
| Capacitor or contactor | $400–$600 |
| Outdoor (condenser) fan motor | $300–$800 ($500–$1,600+ variable-speed) |
| Indoor blower motor | $400–$900 ($800–$2,000 ECM variable-speed) |
| Expansion valve (TXV) | $1,000–$2,500 |
| Compressor | $2,000–$4,500 |
| Reversing valve, defrost board or sensor, refrigerant leak repair | Quoted as a fixed price before we start |
Repairs are quoted as a fixed price before we start, typically based on $150 to $250 per hour plus parts and drive time. For the parts most often behind a no-heat call, see bad capacitor signs, condenser fan motor cost and compressor replacement cost.
Repair or Replace?
Repair usually makes sense for a heat pump under about 10 years old that has had few problems. An older system that needs a compressor, or one that has needed repeated repairs, is worth comparing with a new one: a whole-home ducted heat pump in San Jose typically costs $8,000 to $25,000 before rebates. See the heat pump installation cost guide and how long heat pumps last.
CPI Service repairs and installs heat pumps throughout San Jose and the South Bay. See heat pump installation and repair and mini-splits, request a free estimate or call (408) 978-3093.
Sources
- Lennox: What to Do If Your Heat Pump Is Frozen?
- ENERGY STAR: Air-Source Heat Pumps
- ENERGY STAR: Maintenance Checklist
- EPA: Section 608 Technician Certification
- EPA: Stationary Refrigeration and Air Conditioning (Section 608)
- San José Clean Energy: EcoHome Rebate
Checked October 2026.
Frequently Asked Questions
Why is my heat pump running but not heating the house?
Check the thermostat first: it should be on Heat (not Cool or Auto) and set above room temperature. Then check the air filter and that the outdoor unit isn't blocked or iced over. If those are fine, the usual causes are a defrost problem, low refrigerant from a leak, a stuck reversing valve or a failing outdoor fan, which a technician has to diagnose.
Is it normal for a heat pump to have ice on it?
Light frost on the outdoor coil in cold, damp weather is normal, and the heat pump melts it with a defrost cycle; you may see steam. Lennox says heavy ice that covers the unit, or ice that doesn't clear within several hours, means a problem.
Should I switch my heat pump to emergency heat?
Only as a stopgap. Emergency heat turns off the heat pump and runs the backup heat, which is useful while an iced-over outdoor unit thaws or while you wait for a repair, but backup electric heat uses more electricity for the same warmth than the heat pump does. If you need it for more than a short time, call a technician.
Can I add refrigerant to my heat pump myself?
No. Under EPA Section 608, technicians who service equipment that could release refrigerant must be certified, and venting refrigerant is prohibited. A heat pump that's low on refrigerant has a leak, which needs to be found and fixed, not just topped up.
Why does my heat pump run all the time in winter?
Heat pumps run longer, gentler cycles than furnaces, so long run times alone aren't a problem. If it runs constantly and the house still won't reach the setting, look for a dirty filter, closed vents, leaky ducts, a refrigerant leak or a system that's too small for the house.
How much does heat pump repair cost in San Jose?
It depends on the part. As of October 2026, typical CPI prices are $400 to $600 for a capacitor or contactor, $300 to $800 for an outdoor fan motor, $1,000 to $2,500 for an expansion valve and $2,000 to $4,500 for a compressor. Other repairs are quoted as a fixed price before we start.
Our new heat pump system has just been installed and we are very pleased with CPI and the new equipment. We are especially grateful for the knowledgeable and hard-working technician Bunhak, who worked throughout our recent heatwave to finish the job. We would highly recommend CPI for any HVAC installation or maintenance.
Linda G., Google review
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