Heat Pump Not Heating in Cupertino

Heat Pump Not Heating in Cupertino

Cupertino's climate is mild, with a marine influence and easy winters, so a heat pump here is rarely fighting the cold. When one stops heating, it is not the weather beating the equipment. It is a component fault. On the variable-speed inverter systems common in newer homes, that usually means a sensor, the defrost control, or a fault-code lockout rather than a worn mechanical part.

A heat pump heats by reversing its refrigerant cycle to pull warmth from outdoor air. On an inverter unit the controls are smarter and the failure modes shift with them. A drifting thermistor, a defrost board that misreads coil temperature, or a protective fault code can shut the unit down. The mechanical basics still apply, the reversing valve, the charge, the contactor, but the diagnosis leans on reading the unit's own error history first.

Because the climate is mild, a no-heat call here is almost always one fixable thing. We pull the fault codes, find the failed component, and put the repair on a written estimate. If your equipment is still under a registered manufacturer warranty, we check whether the failed part is covered and tell you what we find.

Common causes

Sensor or thermistor fault. Inverter heat pumps rely on temperature sensors to manage the heating cycle. A drifting or failed thermistor on the coil or discharge line can make the unit cut back or stop heating to protect itself. We read the fault code, check the sensor reading against actual temperature, and replace the sensor.

Defrost control fault. On cool damp Cupertino mornings the outdoor coil frosts and the unit runs defrost to clear it. A defrost board misreading coil temperature lets ice build and heat output drop. We watch a defrost cycle, verify the sensor reads true, and replace the board or sensor.

Communication or fault-code lockout. Modern inverter systems shut themselves down and log a code when they detect a fault, sometimes a comms error between indoor and outdoor units. We read the unit's error history with the manufacturer diagnostics, trace the wiring or board behind the code, and clear it once the root cause is fixed rather than just resetting it.

Stuck reversing valve. Even on newer equipment the reversing valve can fail to shift into heat, leaving the unit blowing cold. We read line temperatures to confirm the valve is not switching, then replace it. On a unit still under a registered parts warranty, the valve itself may be covered, and we check before quoting.

Low refrigerant charge. A leak, usually at a connection, drops heating capacity and can trip a low-pressure fault on these units. We pressure-test, find and repair the leak, and weigh in the correct charge to factory spec, which matters more on inverter systems than on older fixed-speed units.

How we diagnose it

• Pull the unit's fault codes and error history with manufacturer diagnostics before touching anything mechanical.
• Check the coil and discharge thermistors against actual temperature, since sensor drift is a common inverter failure.
• Watch a defrost cycle and inspect the outdoor coil for ice on damp mornings.
• Confirm the reversing valve shifts into heat by reading line temperatures, and verify the charge is at factory spec.
• Confirm warranty status on the equipment so any covered part goes on the estimate as covered.

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

Heat Pump Not Heating in Cupertino: common questions

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Heat Pump Not Heating near Cupertino: Sunnyvale · Saratoga · Los Altos .

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