Your heat pump is running — the indoor blower is going, the outdoor unit is humming — but on a hot inland afternoon the air from the vents is warm and the house keeps climbing. Because a heat pump is your air conditioner and your furnace in one, a no-cool call in July is every bit as urgent as a no-heat call in January, and it usually comes down to a single failed part rather than a dead system.
This page explains what actually makes a heat pump run without cooling, what you can safely check yourself, and when it's time for a licensed tech.
How it usually shows up:
- The system runs constantly but the vents blow warm or barely cool air.
- The house "won't drop below 80°" through the afternoon heat.
- The outdoor unit hums but the fan on top isn't spinning.
- Cooling worked fine last summer and quit without warning this year.
Why your heat pump is blowing warm air in summer
A heat pump cools exactly the way a central AC does, with one extra part that can fail in a way a straight AC never can. Roughly in the order we find them:
- Reversing valve stuck in heating. This is the classic heat-pump-only fault. The reversing valve is what flips the system between heating and cooling; if it sticks or its solenoid fails, the heat pump keeps running in heat mode in the middle of summer and pushes warm air no matter where you set the thermostat.
- Low refrigerant from a leak. A heat pump moves heat with refrigerant and doesn't "use it up" — if it's low, there's a leak. An undercharged system blows warm and often ices up. Refrigerant work is licensed-tech only (EPA 608).
- A dirty or blocked coil. A caked outdoor condenser coil or a dirty indoor coil chokes heat transfer, so the system runs but sheds little heat.
- A dirty air filter. Restricted airflow cuts cooling and can freeze the indoor coil — the cheapest and most common contributing cause.
- Thermostat set or wired wrong. A thermostat left in HEAT, or miswired after a swap, has the system faithfully calling for heat while you wait for cool air.
- A failed capacitor or contactor. The capacitor starts the compressor and outdoor fan; the contactor sends it power. When either fails the outdoor fan won't spin (just a hum) and the compressor can't cool.
- A failing compressor. The high end — if the compressor can't build pressure, everything else runs but no cold is produced.
The usual fix
Our tech starts by confirming the system is actually calling for cooling in the right mode, then checks airflow and refrigerant charge — the two things behind most weak-cooling calls. From there it's usually one of a few paths: clear a dirty filter or coil, replace a failed capacitor or contactor, repair a refrigerant leak and recharge the system to spec, or free or replace a stuck reversing valve. Compressor problems are diagnosed last because they're the costliest and least common. You get a firm quote before any part goes in.
DIY vs. calling a pro — the honest version
Safe to check yourself first (free):
- Set the thermostat to COOL with the set point a few degrees below room temperature and fresh batteries — and make sure it isn't accidentally left in HEAT.
- Change the air filter if it's dirty, and confirm return and supply vents aren't blocked by furniture or rugs.
- Clear the outdoor unit of leaves, cottonwood, and yard debris, and keep a couple of feet of clearance so it can shed heat.
- Rule out a mode mix-up. If the air stays warm no matter the setting and the unit is otherwise running normally, note that for the tech — it points toward the reversing valve.
Call a pro when:
- The air is still warm after a fresh filter and a correct COOL setting.
- The outside fan won't spin or the unit just hums (capacitor/contactor).
- You suspect a stuck reversing valve (warm air in cooling mode) or low refrigerant (icing, weak cooling).
- There's ice on the coil or the copper refrigerant line.
Refrigerant, reversing-valve, and capacitor work carry high pressure and line voltage — this is where a licensed tech pays for itself and keeps the warranty intact.
What it costs in the Bay Area
Heat-pump repairs vary widely by the part. In our pricing, a capacitor runs about $120–$350 — the cheap, common fix. A refrigerant leak repair plus recharge is roughly $180–$700 depending on the leak, and a reversing valve is the high end at $450–$900. We charge a diagnostic fee that's credited toward the repair when you approve the work, and you'll always see a flat, upfront price before we start — no surprise line items.
Get your heat pump cooling again
Triton repairs heat pumps, central AC, and mini-splits across the East Bay, Tri-Valley, and Peninsula — Livermore, Pleasanton, Dublin, San Ramon, and Hayward among the inland cities where summer heat hits hardest. Same-week (often same-day) appointments, upfront pricing, and licensed techs.
Book online or call (888) 993-5699. We'll get a tech out to find the fault and get cold air back.
Related pages
- HVAC Repair in the SF Bay Area — our full heating & cooling hub
- Heat Pump Not Heating / Blowing Cold Air in Winter — the winter, heating-mode version
- AC Not Cooling / Blowing Warm Air — the central-AC version
- Heat Pump Frozen / Iced-Over Outdoor Unit — when the coil ices solid
- HVAC & Heat Pump Repair in Livermore — Tri-Valley service area
Frequently asked questions
Why is my heat pump blowing warm air in cooling mode? The most common heat-pump-only cause is a reversing valve stuck in heating, which keeps the system in heat mode no matter what the thermostat says. Low refrigerant from a leak, a dirty coil or filter, or a failed capacitor can also leave it running without cooling. Set the thermostat to COOL and change the filter first; if the air is still warm, it needs a tech.
What is a reversing valve and can it really get stuck? The reversing valve is the part that switches a heat pump between heating and cooling by changing the direction refrigerant flows. When it sticks or its solenoid fails, the system can get stuck in heat mode and blow warm air all summer. Freeing or replacing it is a licensed-tech repair.
Why won't my heat pump cool the house below 80 degrees? On a hot day a heat pump that's low on refrigerant, has a dirty coil, or is fighting a partly stuck reversing valve simply can't keep up — it runs nonstop and loses ground. If a clean filter and a correct COOL setting don't restore cooling, have the refrigerant charge, coil, and reversing valve checked.
Can a dirty filter stop a heat pump from cooling? Yes. A clogged filter starves the system of airflow, which cuts cooling and can freeze the indoor coil into a block of ice that blocks airflow entirely. Changing the filter is the first thing to try and it's free.
How much does heat-pump cooling repair cost in the Bay Area? It depends on the part: a capacitor is about $120–$350, a refrigerant leak repair and recharge runs roughly $180–$700, and a reversing valve is the high end at $450–$900. We credit the diagnostic fee toward the repair and give you a firm price before any work begins.
Do you offer same-day heat pump repair near me? Yes — we serve the East Bay, Tri-Valley, and Peninsula (Livermore, Pleasanton, Dublin, San Ramon, and Hayward) with same-week and often same-day slots, which matter most during a heat wave. Call (888) 993-5699 to book.