Heat Pump Not Heating in San Mateo
A heat pump that will not heat often comes down to the same reversing valve, only stuck in the other direction, or a defrost cycle that never completes and leaves the outdoor coil iced over. Low refrigerant, a failing outdoor fan motor, or a corroded contactor and capacitor can all shut heating down the same way they would shut down cooling. We check mode, defrost, and charge in that order before opening anything mechanical. The detail that matters in San Mateo is the mix of condos and townhomes alongside older single-family neighborhoods.
Local climate and housing age both matter for a heat pump heating call. San Mateo is the biggest city on this stretch of the Peninsula and runs a real mix of microclimates, from the cooler bayfront near Foster City to the warmer hills around San Mateo Park and the Highlands. The city has more condos and townhomes than most of its neighbors, concentrated around Hillsdale and North Central, alongside older single-family neighborhoods like Baywood and San Mateo Park with original HVAC well past service life. A condo or townhome job usually means a packaged or ductless system and an HOA to coordinate with, a different conversation than a single-family install.
In San Mateo, we check mode, defrost, and refrigerant charge in that order, because a heat pump that won't heat is rarely one single obvious thing. Whatever the sequence turns up goes on a written estimate, and the $99 diagnostic fee is credited toward the repair.
Common causes
Corroded contactor or capacitor on the outdoor unit. The same electrical parts that fail on an AC condenser fail on a heat pump's outdoor unit. Hillsdale-area condos and townhomes commonly run packaged or through-wall equipment with more exposed wiring than a house. A failed capacitor or a pitted contactor keeps the outdoor unit from running at all.
Stuck reversing valve. A reversing valve stuck in cooling mode leaves the system unable to produce heat no matter what the thermostat calls for. It is one of the first things we rule in or out.
Low refrigerant from a corroded coil or fitting. A leak drops the charge low enough that the system cannot pull adequate heat from the outdoor air, and a corroded fitting is a common leak point. Hillsdale-area condos and townhomes commonly run packaged or through-wall equipment with more exposed wiring than a house.
Failed defrost control. In cold, damp conditions the outdoor coil ices over and the system has to periodically defrost it. A failed defrost board or sensor leaves the coil frozen solid, which blocks heat transfer entirely.
Seized or failing outdoor fan motor. Without the outdoor fan moving air across the coil, the system cannot pull heat from the outside air efficiently, and a seized motor is a common, testable failure.
How we diagnose it
- Confirm the thermostat is actually calling for heat and the system is in heat-pump mode, not stuck on emergency or off.
- Read line temperatures at the indoor and outdoor coils to tell whether the reversing valve has actually shifted into heating.
- Meter the capacitor and inspect the contactor for wear. Hillsdale-area condos and townhomes commonly run packaged or through-wall equipment with more exposed wiring than a house.
- Read refrigerant pressures against the outdoor temperature to spot a low charge before chasing the leak.
- Confirm the defrost board initiates a cycle and the outdoor coil is clear of ice.
$99 diagnostic, credited toward the repair. You get a written quote before any work begins.
Heat Pump Not Heating in San Mateo: common questions
We're in San Mateo with a heat pump, not a furnace. Do you still cover that?
We're in a condo near Hillsdale with a packaged unit, not a house with a normal system. Does that change how you handle it?
The outdoor coil is covered in ice and it never seems to clear on its own. Is that a defrost problem?
Nearby and related
Heat Pump Not Heating near San Mateo: Burlingame · Belmont · Foster City .
This is usually a heat pump installation & service in San Mateo job. See our heat pump installation & service overview or the San Mateo service area.
Heat Pump Not Heating in San Mateo
Repairs start with a $99 diagnostic, credited toward the fix. Replacing a system? The on-site assessment visit is free. Same-day written findings either way.
Bay Area · 7am–7pm · 7 days · no overtime charges