AC Freezing Up in Menlo Park

AC Freezing Up in Menlo Park

An AC coil freezes when its surface drops below 32 degrees and the moisture in the passing air condenses and freezes onto it. The system needs a steady flow of warm room air across that coil to stay above freezing. Restrict the airflow, or let the refrigerant charge fall low, and the coil temperature crashes. Ice forms, and the ice itself blocks more air until you have a solid frost block on the coil and the suction line.

Menlo Park has some of the mildest summers on the Peninsula, with a real marine layer most mornings. That matters for diagnosis. Your AC is not failing because it is overworked. When a Menlo Park coil freezes, the cause is mechanical: a clogged filter, a weak blower, a dirty coil, or a slow refrigerant leak. The mild climate rules out the 'it just ran too hard' explanation almost every time.

There is a sizing wrinkle here too. Because the climate is so mild, a fair amount of equipment in older Menlo Park homes was sized for the coldest design day on the heating side and ends up oversized for the cooling load. An oversized unit short-cycles and never fully dehumidifies, and paired with marginal ducting it can freeze a coil on a system that looks fine on paper.

Common causes

Dirty air filter. The most common and cheapest cause. A loaded filter starves the coil of warm airflow and drops it below freezing. We replace it and verify the coil temperature split returns to spec before looking further.

Low refrigerant from a slow leak. A low charge lowers coil pressure until it freezes, and the mild summers here mean a slow leak can go unnoticed for a season. We leak-test electronically, repair the leak, and recharge to the manufacturer's subcooling or superheat target instead of just topping it off.

Restricted or marginal ductwork. In older Peninsula homes where AC was retrofitted onto existing ducts, the return path is often undersized. We measure static pressure to find the restriction and tell you honestly whether it is a grille and damper fix or a real duct limitation.

Oversized equipment short-cycling. An AC too large for a mild-climate home cycles on and off too fast to keep airflow stable across the coil, which can trigger freezing. We confirm sizing against the home's actual load and, on a replacement, size the equipment to the climate so it does not happen again.

Dirty evaporator coil. Dust caked on the coil fins insulates and restricts airflow even with a clean filter. We open the air handler, inspect the coil, and clean it correctly rather than just thawing the surface and leaving the buildup in place.

Failing blower or stuck relay. If the blower motor, its capacitor, or the relay that starts it is weak, the coil loses airflow and freezes. We read blower amperage and confirm the blower actually starts with the cooling call. A bad capacitor or stuck relay is a modest fix; we put the number on the estimate first.

How we diagnose it

• Shut the cooling off and let the coil thaw fully so readings reflect the real running condition.
• Inspect the filter and return path, then measure static pressure to catch undersized or restricted ductwork common in older Menlo Park homes.
• Read suction pressure, subcooling, and superheat on gauges to separate an airflow cause from a low refrigerant charge.
• Check equipment sizing against the home's load, since oversizing is a more frequent mistake than undersizing in this climate.
• Inspect the evaporator coil and verify the blower and its relay deliver full airflow.

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

AC Freezing Up in Menlo Park: common questions

Nearby and related

AC Freezing Up near Menlo Park: Palo Alto · Los Altos .

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