AC Freezing Up in San Leandro
San Leandro sits in a mild East Bay band, with bay-side highs in the 70s to mid 80s and warmer pockets inland. AC runs moderately here, so freeze-ups tend to show up on the warmer inland days or on aging systems whose airflow was marginal to begin with. Ice on the evaporator coil or a frosted refrigerant line means the coil is running colder than the air moving past it, and on a lot of San Leandro homes that airflow problem traces straight back to the ductwork.
Much of the city is 1950s through 70s suburban single-family, and a good share of that housing is on its second or third AC system bolted onto original ducts. Leaky or undersized returns starve the coil, it ices, and the homeowner assumes the AC died. It usually did not. The freeze is almost always one fixable thing: a clogged filter, a restricted return, a tired blower, or a charge that leaked down on an older R-22 or early R-410A system.
Whatever the cause, the unit has to thaw first so the compressor never pulls liquid refrigerant and the pan does not overflow. We clear the ice, then read the system and the duct airflow together, because in this housing stock they often turn out to be the same problem.
Common causes
Leaky or undersized original ductwork. San Leandro's original ducts often leak badly enough to starve the coil and ice it. We measure the actual duct leakage on the diagnostic, and if it is the cause we tell you whether sealing fixes it or whether the return side needs to be opened up to feed a modern system.
Dirty air filter. The simplest and most common. A clogged filter cuts airflow across the coil until it freezes. We check it first, read static pressure across the coil, and show you the number before we look further.
Low refrigerant on an aging system. Many late-90s and early-2000s San Leandro systems are still running, and a slow leak drops the charge until the coil freezes. We leak-test and repair, then recharge to spec. On an R-22 system we run the replacement numbers, because reclaimed R-22 is uneconomical for ongoing repair.
Weak blower motor. A blower that has lost speed over the decades moves less air every cycle and lets the coil ice. We measure actual CFM and the motor's amp draw against spec, and check the capacitor. Often it is a cheap capacitor, sometimes it is a motor near the end.
Dirty evaporator coil. On homes where the coil has never been pulled and cleaned, dust on the face insulates it and drives it below freezing. We inspect and clean the coil when it is loaded, which also restores the efficiency the system lost along the way.
How we diagnose it
- Shut the cooling down and confirm full thaw before running it, so the compressor never ingests liquid refrigerant.
- Inspect the filter and read coil static pressure to confirm whether airflow is the restriction.
- Measure duct leakage, since failing original ductwork is a frequent root cause in this housing stock.
- Gauge the system for superheat and subcooling to separate an airflow freeze from a low-charge freeze, and leak-test if it reads low.
- Measure blower CFM, amp draw, and capacitor, and inspect the evaporator coil face.
$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.
AC Freezing Up in San Leandro: common questions
Do you service San Leandro, or only the Tri-Valley side of the Bay?
If my ductwork is the problem, am I looking at a huge bill?
The line going into the house is covered in frost. Is that the same as the coil freezing?
Nearby and related
AC Freezing Up near San Leandro: Oakland · Hayward · Castro Valley .
This is usually a ac repair in San Leandro job. See our ac repair overview or the San Leandro service area.
AC Freezing Up in San Leandro
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