Heat Pump Not Cooling in Moraga, CA | Bay Area HVAC Service

Heat Pump Not Cooling in Moraga

A heat pump runs the same refrigeration cycle as an AC, with a reversing valve added so the system can heat in winter and cool in summer. When a Moraga heat pump runs but will not cool, we work it as a cooling failure first and check the reversing valve as the one part a straight AC does not have.

Moraga's valley microclimate swings from cool, foggy mornings to warm afternoons in the 82-to-90 range. That daily swing is generally kind to heat pumps, which is why they run efficiently here, but it also means a marginal system can cool fine in the morning and then fall behind once the afternoon heat lands. A complaint that comes and goes with the time of day often points to a charge or airflow problem rather than a total failure.

A heat pump that still powers on and blows air almost always has a healthy compressor and fan, the expensive parts. The real fault is one component, usually a worn capacitor, a slow leak, a fouled coil, or a stuck reversing valve. We find the part, write the price on the estimate, and give you an honest repair-or-replace read given the system's age and the larger lots common here.

Common causes

Reversing valve stuck in heat mode. The reversing valve flips a heat pump between heating and cooling. If it or its solenoid sticks, the unit keeps running in heat and blows warm air when you call for cool. We confirm it with line-temperature readings and by listening for the valve to shift on a mode change, then replace the solenoid coil or the valve itself, whichever actually failed.

Low refrigerant from a leak. A slow leak shows up as cooling that fades in the afternoon heat, a frosted suction line, and run times that never satisfy the thermostat. We measure superheat and subcooling, find the leak with a detector or dye, repair it, and recharge to spec. Topping off a leaking system only postpones the next no-cool call.

Failed run capacitor or contactor. The capacitor starts the compressor and outdoor fan, and the contactor is the relay that powers the outdoor unit. A weak capacitor stalls the fan or makes the compressor hum and trip; a pitted contactor drops power intermittently. Both are common, inexpensive, and carried on the truck.

Dirty outdoor coil. Moraga's wooded, larger lots drop leaves and pollen straight into outdoor coil fins. A clogged coil cannot reject heat, so the unit runs nonstop and the house never cools. We wash the coil and recheck the temperature split to confirm recovery.

Frozen indoor coil from low airflow. Cool, damp morning air plus a dirty filter or weak blower can ice the indoor coil, after which almost no cooling reaches the rooms. We thaw the coil, find the airflow restriction, and fix the cause so it does not re-freeze the next warm afternoon.

Hillside condenser placement issues. Many Moraga homes sit on hillside lots where the condenser is tucked against a slope or fence with poor clearance. Restricted airflow around the outdoor unit makes it recirculate its own hot exhaust and lose cooling capacity. We check clearances and discharge airflow, and on installs we scope placement carefully so the unit can actually breathe.

How we diagnose it

Confirm the thermostat is calling for cool and the reversing-valve signal is energizing at the board.
Verify the outdoor unit starts cleanly: capacitor, contactor, compressor, and condenser fan.
Read refrigerant pressures, superheat, and subcooling to separate a leak or low charge from a stuck valve.
Check outdoor-unit clearances and the coil for the airflow restrictions common on hillside lots, plus the indoor coil and filter.
Measure the temperature split across the indoor coil to confirm cooling is genuinely restored before we leave.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

Heat Pump Not Cooling in Moraga: common questions

Do you serve Moraga, or is it outside your range?

We cover Moraga along with Orinda and Lafayette as part of our regular Lamorinda route from San Ramon. It is a straightforward run for us. Call (925) 999-4095 and we will give you an honest arrival window and tell you whether we can reach you the same day.

Why does my Moraga heat pump cool fine in the morning but not in the afternoon?

That pattern fits Moraga's climate. Cool foggy mornings hide a weak system, then the afternoon heat in the high 80s exposes it. It usually means a low refrigerant charge or restricted airflow, both of which leave just enough capacity for a mild morning and not enough for peak heat. We measure the charge and airflow to confirm which it is.

My heat pump runs but blows warm air. Is the whole system shot?

Rarely. Warm air from a running heat pump most often means a reversing valve stuck in heat, a low charge, or a thermostat in the wrong mode, none of which is a dead compressor. We diagnose for $75, credited toward the repair when it is over $200, and we identify the exact failed part before any work starts.

Nearby and related

Heat Pump Not Cooling near Moraga: Orinda · Lafayette .

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