Heat Pump Not Heating in Danville

Heat Pump Not Heating in Danville

A heat pump that stops heating in Danville is almost never a dead system. Our winters are mild, well inside the range a properly charged heat pump handles. When it suddenly runs cold air, one specific part has usually failed, and the rest of the system is fine. The trick is identifying which part before anyone talks about replacement.

We see two broad versions of this in Danville. On the older ranches, where a homeowner converted a 1970s gas furnace to a heat pump, the recurring faults are a stuck reversing valve or a weak start capacitor on an outdoor unit that has aged through several seasons. In the newer custom homes running dual-zone, dual-stage equipment, it is more often a control-board or zone-damper problem where the call for heat never reaches the compressor, or the backup heat strips never stage in.

We diagnose to the component. We confirm whether the heat pump actually reverses to heating, measure whether the refrigerant charge holds, and watch whether the defrost board cycles. Each of those is a reading, not a guess, and each goes on the written estimate with what it costs to fix.

Common causes

Reversing valve stuck in cooling. The reversing valve is what flips a heat pump between cooling and heating. When it sticks or its solenoid coil fails, the unit keeps running in cooling mode in winter and blows cold air. We check the coil for continuity and listen for the valve to shift on a mode change. A failed solenoid is a part swap; a mechanically seized valve is a larger refrigerant job, and we tell you which one you have before quoting.

Low refrigerant charge. A heat pump moves less heat as charge drops, so it runs long and never warms the house. On the older converted systems, a slow line-set leak is a common cause. We put gauges on it, check subcooling and superheat against the unit spec, and find the leak rather than just topping it off. A recharge without a leak repair is money wasted in a season.

Defrost control fault. In heating mode the outdoor coil frosts, and the defrost board is supposed to clear it on a timed or demand cycle. A failed board or sensor lets ice build until the unit can no longer pull heat from outside air. We watch a defrost cycle run, test the sensor, and replace the board if it is not commanding defrost on schedule.

Backup heat strips not staging in. Many Danville heat pumps have electric backup heat for cold mornings and defrost cycles. When the strips, their sequencer, or the relay fail, you get cold air during defrost or on the coldest mornings while the compressor catches up. We confirm the strips draw current when called and that the control logic stages them at the right outdoor temperature.

Contactor or start capacitor failure. A pitted contactor or a weak start capacitor keeps the outdoor compressor from running at all, so the indoor blower moves unconditioned air. These are common wear items on aging converted systems. We measure the capacitor against its rating and inspect the contactor contacts; both are stocked parts we carry on the truck.

Zone control or thermostat fault. On the dual-zone systems in the newer custom homes, a failed zone board, stuck damper, or miswired smart thermostat can leave one zone calling for heat that the equipment never receives. We meter the call at the board, cycle each damper, and verify the thermostat is actually sending the heating signal before touching the equipment.

How we diagnose it

• Confirm the thermostat is calling for heat and the reversing valve actually shifts the system into heating mode on that call.
• Put gauges on the unit and read subcooling and superheat against the equipment spec to confirm charge and catch a line-set leak.
• Run a full defrost cycle and test the defrost board and coil sensor for correct timing.
• Check that backup heat strips draw current and stage in at the right outdoor temperature.
• On multi-zone homes, meter the heat call at the zone board and cycle each damper to rule out a control-side fault.

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

Heat Pump Not Heating in Danville: common questions

Nearby and related

Heat Pump Not Heating near Danville: San Ramon · Alamo · Blackhawk · Walnut Creek · Pleasanton .

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