AC Not Cooling in Concord

AC Not Cooling in Concord

Concord puts more load on an AC than almost anywhere else we serve. Summer afternoons routinely run in the 90s with hotter stretches during heat waves, so a system that was quietly failing all spring chooses the hottest day to give up. The reassuring part is that 'not cooling' here is overwhelmingly a single worn part. From late spring through summer, our most common Concord call is a degraded capacitor, because sustained high heat ages them faster than spec. We carry them on every truck.

After capacitors, the usual suspects are low refrigerant from a leak, a pitted contactor, a dirty condenser coil that cannot shed heat in hot air, and a frozen evaporator coil from a clogged filter starving airflow. Much of Concord is tract construction from the postwar decades, and a lot of that equipment is in its second or third replacement cycle. Aging systems leak and wear, but they rarely die outright on the first warm call.

We measure the system's real refrigerant pressures and temperatures before quoting. Where we do find a true end-of-life problem, often an R-22 leaker, we run the replacement numbers honestly rather than selling a repair that will not hold.

Common causes

Failed run capacitor. The signature Concord summer failure. The compressor hums but will not start, or short-cycles. Sustained high heat ages capacitors faster than rated. We test microfarads and replace it, typically $150 to $250 installed, same visit. It is the first thing we check during the hot months.

Low refrigerant from a leak. The unit runs nonstop in the heat and the air is only mildly cool. We measure superheat and subcooling, find the leak with electronic detection, and write up the repair and recharge separately. On R-22 systems we run replacement numbers, since reclaimed R-22 is expensive enough to make repair uneconomical on old equipment.

Pitted contactor. The relay that energizes the condenser pits and fails on systems past 8 years, and the outdoor unit will not start in the heat. We inspect and replace it, a quick fix that also prevents the burnt contacts from taking the compressor with them.

Dirty condenser coil. When it is hot out, an outdoor coil caked with dust cannot reject heat, and cooling falls off exactly when you need it most. We wash the coil and recheck head pressure. Concord's hot, dusty summers make this a recurring cause, and a clean coil eases load on every other part.

Frozen evaporator coil from low airflow. A clogged filter or weak blower starves the indoor coil until it ices over, and then the system blows warm even though it is running hard. We thaw it, find the airflow restriction, and fix the cause so it does not refreeze when the next hot day arrives.

Oversized, short-cycling equipment. Many older Concord installs were oversized by tonnage rather than load, so they short-cycle and never properly dehumidify or hold temperature. When we replace, we run a Manual J calculation to right-size, which cuts operating cost and stops the short-cycling for good.

How we diagnose it

• Test the capacitor first, since it is the dominant Concord cooling failure in summer heat.
• Read refrigerant pressures and temperatures with gauges, and check whether the system runs R-22.
• Inspect the contactor for pitting and confirm the condenser energizes.
• Wash and inspect the condenser coil and check the indoor coil and filter for airflow restriction.
• On replacement estimates, run a Manual J load calculation rather than matching old tonnage.

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

AC Not Cooling in Concord: common questions

Nearby and related

AC Not Cooling near Concord: Walnut Creek · Martinez .

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