Heat Pump Not Cooling in South San Francisco

Heat Pump Not Cooling in South San Francisco

A heat pump that will not cool is usually stuck in the wrong mode or short a working part, not finished. The reversing valve has to actually shift into the cooling position, the refrigerant charge has to be correct, and the same capacitor, contactor, and airflow issues that affect any AC apply here too. We confirm the thermostat is calling for cooling and the valve has actually shifted before chasing anything else. The detail that matters in South San Francisco is the fog-line split between the old flatland neighborhoods and hillside Westborough.

Local climate and housing stock both shape a heat pump call here. South San Francisco sits under heavy fog for much of the year, especially in the older flatland neighborhoods below Sign Hill, while newer construction up in Westborough sits above the fog line and runs noticeably warmer. Neighborhoods like Winston Manor and Sunshine Gardens carry a lot of older housing built without ductwork, since nobody needed central air under that much fog. Westborough's newer hillside construction is a different story, built later and with more real cooling load to plan around.

In South San Francisco, we confirm mode and valve position before opening anything mechanical, because a heat pump stuck in the wrong mode looks identical to a real failure from the thermostat. The actual fault goes on a written estimate, and the $99 diagnostic fee is credited toward the repair.

Common causes

Reversing valve stuck in heat mode. The reversing valve is what lets a heat pump run in both directions, and a valve stuck in heating mode leaves the system blowing warm air no matter what the thermostat says.

Low refrigerant from a leak. The same low-charge problem that affects a standard AC applies to a heat pump running in cooling mode. We find the leak rather than top off the charge and hope.

Corroded contactor or failed capacitor. The outdoor electrical components on a heat pump face the same wear as any AC condenser. The damp, fog-heavy air here still works its way into loose or aging connections over time, even without direct salt exposure. We test both before condemning anything bigger.

Dirty or fouled outdoor coil. A coil that cannot reject heat properly in cooling mode leaves the house warm even with everything else working. Cleaning it is a cheap first step that often restores lost capacity.

Frozen indoor coil from low airflow. A restricted filter or return chokes airflow enough to ice the indoor coil, which then blows warm air exactly like a standard AC in the same situation.

Thermostat in the wrong mode. Some heat pump thermostats and controllers make it easy to end up in a heat-only or auto-changeover mode that will not call for real cooling. We verify mode settings before any mechanical diagnosis.

How we diagnose it

• Confirm the thermostat is actually calling for cooling and the reversing valve is commanded to the cool position.
• Read suction and liquid line temperatures and pressures to see whether refrigerant is flowing the right direction and the charge is correct.
• Test the run capacitor against its rated microfarads and inspect the contactor for wear. The damp, fog-heavy air here still works its way into loose or aging connections over time, even without direct salt exposure.
• Inspect and clean the outdoor coil, and check the indoor coil and filter for ice or restricted airflow.
• Put the actual fault and the repair on a written estimate before any parts go in.

$99 diagnostic, credited toward the repair. You get a written quote before any work begins.

Heat Pump Not Cooling in South San Francisco: common questions

Nearby and related

Heat Pump Not Cooling near South San Francisco: San Bruno · Daly City · Millbrae .

This is usually a heat pump installation & service in South San Francisco job. See our heat pump installation & service overview or the South San Francisco service area.