Refrigerant carries heat out of your house in summer and, in a heat pump, into it in winter. It moves in a sealed loop and does not get used up, so a system in Daly City that is low on refrigerant has a leak, and near the coast the outdoor coil is a frequent suspect. This service covers air conditioners and heat pumps: leak detection, leak repair and recharging to the manufacturer’s specification. Most visits take one to four hours.
Signs the charge is low
- AC not cooling adequately. Long run times, and air from the vents that is cool rather than cold.
- Ice formation on refrigerant lines. Frost on the larger copper line or on the indoor coil.
- Hissing or oily spots. Refrigerant carries oil, so a leak often leaves a greasy patch at a fitting or on a coil.
- A heat pump that heats poorly. Heat pumps here run most of the year, so a slow leak often shows first as weak heat in winter. See heat pump repair.
- Rising bills. A short-charged system runs longer for the same result; high energy bills lists other causes.
Why a top-off alone costs more over time
Many compressors are cooled by the refrigerant gas returning to them. With too little charge the compressor runs hot, and repeated overheating shortens its life. Topping off a leaking system restores cooling for a while, then you pay again, and the compressor carries the strain in between. Compressor protection is the real reason to find the leak.
How we find the leak
- Pressure testing. Readings against indoor and outdoor conditions confirm the charge is actually low and that the symptom is not an airflow problem.
- Electronic leak detector. Moved slowly along coils, valves, brazed joints and fittings.
- UV dye. For slow leaks a detector cannot pin down. The dye travels with the oil and glows at the leak under a UV lamp, sometimes on a follow-up visit.
- Bubble solution. To pinpoint a suspected fitting.
- Nitrogen standing test. An empty system is filled with dry nitrogen and watched for a pressure drop.
Where leaks tend to show up here: corroded joints on outdoor coils exposed to salt air, valve cores and caps, flare connections on mini-splits, pinholes in older indoor coils, and line sets that rub against a wall, a bracket or each other.
Repair, evacuate, recharge
- Recover any refrigerant left in the system. Venting it is illegal, and only EPA-certified technicians may open the circuit.
- Repair the leak: braze a joint, replace a valve core, remake a flare or replace the failed part.
- Pressure test with nitrogen to prove the repair holds.
- Evacuate with a vacuum pump to remove air and moisture, then confirm the vacuum holds.
- Recharge by weight to the manufacturer’s specification, then check superheat or subcooling with the system running.
Last, we check airflow and the temperature drop across the coil, so the system is tuned as a whole rather than just refilled.
Which refrigerant is in your system
The nameplate on the outdoor unit lists the refrigerant type and the factory charge.
| Refrigerant | Where you find it | What it means for service |
|---|---|---|
| R-22 | Most systems installed before about 2010 | No longer produced or imported in the US; recovered supply only, at a high price |
| R-410A | Most systems from about 2010 into the mid-2020s | Widely serviced; being phased down, still available for repairs |
| R-32 or R-454B | Newer equipment | Lower-impact refrigerants classed as mildly flammable; serviced with tools rated for them |
When a recharge is not the answer
- A leaking coil. If the leak is in the indoor or outdoor coil itself, the fix is a new coil, quoted separately in writing. On an older R-22 system, that is the point where replacement deserves a look.
- Ice from low airflow. A clogged filter or a dirty indoor coil can freeze a fully charged system. A new filter and coil cleaning fix that, while adding refrigerant would overcharge it. Our page on a frozen AC coil explains how to tell the two apart.
Price
Most refrigerant services run $200 to $800, depending on the refrigerant, how much is needed and how long the leak takes to find and repair. The estimate comes in writing before work starts, and the repair carries a warranty on parts and labor.