AC Not Cooling in Union City, CA | Bay Area HVAC Service

AC Not Cooling in Union City

Union City doesn't get the brutal inland heat of the Tri-Valley, but it's no fog belt either. Summer highs run into the 80s inland, warmer in the Decoto neighborhoods than nearer the bay, and that's plenty to expose an AC that's quietly failing. The typical call: the system runs, the thermostat is set low, but the air is warm or only mildly cool and the house won't come down.

Much of Union City is suburban tract housing built from the 1970s into the 90s, and plenty of those AC systems are well into their second or third decade. At that age the parts that wear out are predictable. A capacitor swells. A contactor pits. Refrigerant works its way past an aging joint. Those are the exact failures that get fixed in one visit. A system that won't cool on a warm afternoon is most often one tired component, not a dead machine.

The one case where it isn't a quick fix is an old R-22 system that has leaked down. R-22 hasn't been produced new in years, the reclaimed supply that's left is expensive, and a system old enough to run it will leak again. When we find that, we say so and lay out repair versus replacement with real numbers, so the decision is yours.

Common causes

Failed run capacitor. The most common reason an aging tract-home AC runs but won't cool. The capacitor that starts the compressor and fan weakens with age and heat, so the system energizes but can't do its job. We meter it and replace it the same visit, usually $150 to $250.

Pitted or burned contactor. On systems past their first decade, the contactor's contacts pit from years of cycling. The compressor then won't pull in reliably or cuts out under load. We test it energized and swap it when the contacts are spent.

Low refrigerant from a leak. An older system that's slowly lost charge can't absorb heat, so the air comes out warm while the unit runs. We read superheat and subcooling rather than guessing, find the leak, and tell you whether it's worth sealing. On R-22 systems a repair often just buys a little time, and we say so.

Dirty or restricted condenser coil. Years of dust and yard debris pack the outdoor coil and choke off heat rejection, which drives cooling capacity down. We clean the coil and check airflow clearance around the unit. On a warm inland afternoon this alone can be the difference between cool and warm vents.

Frozen evaporator coil. A clogged filter or weak blower starves the indoor coil, it ices up, and airflow at the vents drops to nothing. We thaw it, confirm the airflow cause, and fix the filter, blower, or duct restriction behind it instead of just scraping off the ice.

Compressor not starting on an old system. If the compressor itself won't run, we first rule out the cheap causes like a bad capacitor, a pitted contactor, or burnt wiring before condemning it. A genuinely failed compressor on a system this old usually points toward replacement, and we put both paths on the estimate with numbers.

How we diagnose it

Confirm the system is actually cooling by measuring the temperature split across the indoor coil, not by feel.
Meter the capacitor and test the contactor under load.
Put gauges on the refrigerant and calculate superheat and subcooling to separate a charge issue from a leak.
Identify the refrigerant type, because an R-22 system changes the repair-versus-replace math.
Check filter, blower, and coil for ice or airflow restriction.

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

AC Not Cooling in Union City: common questions

Do you actually cover Union City, or just the Tri-Valley?

We cover Union City and the inner East Bay along with Fremont, Newark, and Hayward, dispatched from our San Ramon base. Same-day is our usual target on no-cool calls, not a guarantee. Call (925) 999-4095 and we'll give you a straight answer on timing for today.

My AC is decades old and won't cool. Is it worth repairing?

Often, yes. A capacitor or contactor on a sound older system is cheap insurance. The math flips if it's an R-22 system that has leaked down, since reclaimed R-22 is expensive and the leak tends to come back. We give you the repair and replacement numbers side by side at the estimate and let you decide.

The air coming out is warm, not merely weak. What does that mean?

Warm air with the compressor running usually points to a refrigerant or compressor problem rather than airflow. We confirm it with gauges and a temperature split before naming a cause. If it's a frozen coil instead, you'll often see weak airflow first, then warm air after it fully ices over.

Nearby and related

AC Not Cooling near Union City: Fremont · Newark · Hayward .

This is usually a ac repair in Union City job. See our ac repair overview or the Union City service area.