Heat Pump Not Cooling in Union City, CA

Heat Pump Not Cooling in Union City

Union City sits in a mixed climate, cooler near the bay and warmer as you move inland toward Decoto and the central neighborhoods. Summers reach the 80s and low 90s, hot enough that a heat pump losing its cooling gets noticed quickly. When the system runs and the air coming out is not cold, the cause is almost always one component, not the whole machine.

A heat pump cools on the same cycle as a regular air conditioner. A reversing valve flips it into heating in winter. So we troubleshoot a no-cool heat pump the way we troubleshoot an AC: charge, capacitor, contactor, coils, airflow, then a look at the reversing valve. The fact that it still heats fine in winter tells us most of the system is healthy.

Union City's housing stock is the real context here. A lot of it is older tract construction, and many of those HVAC systems are on their first or second replacement and well past the typical service life. On equipment that age, the parts that wear out are the electrical starting components and the coil fins, which are exactly the parts behind a no-cool call. We carry those parts on the truck.

Common causes

Failed run capacitor. On aging Union City systems this is the single most common no-cool cause. The capacitor that starts the compressor and condenser fan loses capacitance with age and heat. The fan may run slow or the compressor may hum and shut off on overload. We test it against the microfarad rating stamped on the part and replace it if it is out of spec. It is an inexpensive, fast fix.

Worn or pitted contactor. The contactor is the relay that powers the outdoor unit. After years of cycling, the contacts pit and arc, and the unit either will not energize or chatters. On older equipment we see this constantly. We inspect the contacts and swap the contactor when they are burned, which restores reliable starting.

Low refrigerant from a leak. A heat pump that is low on refrigerant has a leak, since the system is sealed and does not burn it off. We measure superheat and subcooling, then find the leak with a detector before adding anything. On older line sets in this housing stock, leaks often show up at flare fittings or aged coils. We tell you whether the leak is worth repairing or whether the coil is at end of life.

Reversing valve stuck in heat mode. If the unit heats but will not cool, the reversing valve may be hung up or its solenoid may have failed. We check the solenoid for voltage and confirm the valve shifts on a cooling call. A bad solenoid is a straightforward replacement. A stuck valve is a larger job, and we put the honest assessment on the estimate either way.

Dirty outdoor coil. Years of dust and yard debris coat the condenser coil, and a blocked coil cannot shed heat. Head pressure rises and cooling falls off. On older units that have never been cleaned, a coil wash is sometimes the entire fix. We check it early because it is the cheapest thing that could be wrong.

Frozen indoor coil from low airflow. A clogged filter or a tired blower motor starves the indoor coil of airflow and it freezes over. Iced coils stop cool air at the registers. We look for ice, thaw the coil, then correct the airflow restriction so it does not freeze again the next hot day.

How we diagnose it

Test the run capacitor against its rated microfarads, since on this older tract stock a weak capacitor is the most likely culprit.
Inspect the contactor contacts for pitting and confirm the outdoor unit energizes and the compressor and fan start.
Read superheat and subcooling to assess charge, and trace any leak on the older line sets rather than just adding refrigerant.
Check both coils and the filter for blockage or ice, since either one cuts cooling while the system appears to run.
Confirm the reversing valve shifts on a cooling call when the unit heats but will not cool.

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

Heat Pump Not Cooling in Union City: common questions

Do you serve Union City directly, or only the Tri-Valley?

We work the whole Bay Area from our San Ramon base, including Union City, Fremont, Newark, and Hayward. Same-day is our best effort and depends on the day's schedule, not a guarantee. Call (925) 999-4095 and we will tell you a realistic arrival window.

My system is over 25 years old and won't cool. Is it worth repairing?

Often the immediate fix is cheap, a capacitor or contactor, and we will do exactly that if it makes sense. But on equipment past 25 years we will also tell you honestly where the rest of the system stands so you can decide. Our diagnostic is $75, credited toward any repair over $200, so you are not paying twice to find out what is going on.

The heat worked all winter but now it won't cool. Why?

That points first at the reversing valve, the only part that changes role between heating and cooling. We test the solenoid and confirm the valve is shifting. Before that, we check the thermostat's mode setting, because a misconfigured heat-pump thermostat can call for cool while the system stays in heat, and that costs nothing to rule out.

Nearby and related

Heat Pump Not Cooling near Union City: Fremont · Newark · Hayward .

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