Evaporator and condenser coil service in San Mateo County
AC iced up or not cooling? Check the coils.
An AC has a coil inside, the evaporator, and a coil outside, the condenser. We clean them, repair them and replace the evaporator coil when it has failed, and a coil replacement brings a duct test with it under the Energy Code.
What coil service involves
The coils do opposite jobs. The evaporator coil indoors absorbs heat from your air, and the condenser coil outdoors releases it. If either one can't do its job, the house stays warm.
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We find which coil is the problem
Ice on the indoor coil, a dirty outdoor coil and a leaking coil can look alike from the thermostat. We read temperatures and pressures to tell them apart.
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Condenser coil cleaning
The outdoor coil is cleaned from the inside out, so dirt is pushed out of the coil and not deeper into it. Cottonwood, grass clippings and dust are the usual culprits.
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Evaporator coil cleaning or replacement
Light dirt can sometimes be cleaned. A coil that has corroded or leaks refrigerant is replaced, and the connections are made to the existing system.
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Test, recharge and run
After a replacement the system is evacuated, charged to its requirement and run through a full cycle, with the readings checked.
How do I know a coil is the problem?
- Ice on the copper line or the indoor coil, even though the AC is running.
- Water pooling at the indoor unit when the ice melts.
- Warm air from the vents, or air that is only slightly cool.
- A very dirty outdoor coil: grey with dust, packed with leaves or cottonwood fluff.
- A refrigerant leak that was traced to the coil and keeps returning.
A dirty coil is a maintenance problem. A leaking coil is a repair problem. Both are quicker to sort out when they are found early.
Should the coil be cleaned or replaced?
Clean when the coil is sound and only dirty: a condenser coil can almost always be cleaned. Replace when the evaporator coil leaks, is corroded or won't stay clean.
A replacement coil has to match your outdoor unit and the refrigerant it uses, so it is not an off-the-shelf swap. If the outdoor unit is old as well, it can be worth pricing the whole system, since the duct and paperwork requirements are the same for either.
Does replacing an evaporator coil need a permit or a duct test?
It needs a duct test. Under the state Energy Code, installing or replacing a cooling or heating coil means the connected ducts must be sealed by the installer and checked by an independent ECC-Rater, the same as for a new outdoor unit or air handler.
Whether the job needs a city permit is up to the city's building department, and the answer differs between cities. Our permit guide lists what each city asks for.
Source: California Energy Commission, 2025 Single-Family Residential Compliance Manual (June 2025), checked 2026-10-17
Think it's a coil?
Call and describe what the AC is doing, or book a visit online.
How do I keep the coils clean?
Change the filter on schedule, because a clogged filter lets dirt reach the indoor coil. Keep the outdoor unit clear of plants and stored items, and have both coils looked at on the yearly tune-up.
Tell us what it's doing. We'll take it from there.
Call and describe the problem: the noise, the smell, the room that never warms up. Or book a visit online.
