Heat Pump Not Heating in Belmont

Heat Pump Not Heating in Belmont

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 Belmont is the ridge-to-flat temperature swing and the long hillside line-set runs.

Local climate and housing age both matter for a heat pump heating call. Belmont sits in the hills between San Carlos and San Mateo, and the microclimate shifts fast within just a few blocks. The flats near El Camino Real stay mild and marine-influenced, while homes higher on the ridge run several degrees warmer and catch more direct afternoon sun. Housing runs from 1940s and 50s ranches on the valley flats to custom hillside homes built from the 1960s through the 80s along the ridge roads above Belmont Heights and Sterling Downs. The hillside homes often have long, steep line-set runs and equipment set on terraced pads, which changes how a repair or install gets staged compared with a flat, easy-access lot.

In Belmont, 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. Hillside homes here often run long wiring and line-set runs, which gives corrosion and chafing more places to start. 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. Hillside homes here often run long wiring and line-set runs, which gives corrosion and chafing more places to start.

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. Hillside homes here often run long wiring and line-set runs, which gives corrosion and chafing more places to start.
• 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 Belmont: common questions

Nearby and related

Heat Pump Not Heating near Belmont: San Carlos · San Mateo · Foster City .

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