Refrigerant is what carries heat out of your house. It circulates in a sealed loop, evaporating in the indoor coil as it soaks up heat and condensing in the outdoor coil as it gives that heat away, and in a healthy system the charge never runs out. So when a system is low, refrigerant has escaped somewhere. Most leaks are slow: cooling fades over weeks or months, the system runs a little longer each afternoon, and one warm day it simply cannot keep up.
Signs of a leak
- Cooling that has weakened gradually, season over season or week over week.
- An AC or heat pump that runs much longer than it used to, with bills creeping up.
- Ice or frost on the larger copper line or on the indoor coil.
- A hissing or bubbling sound near the indoor coil, the outdoor unit or the line set.
- Oily residue at a fitting, a valve or a spot on a coil. Refrigerant carries compressor oil, and where it escapes the oil stays behind and collects dust.
- On a heat pump, weaker heat in winter as well as weaker cooling in summer.
Where leaks happen
| Location | Why it leaks |
|---|---|
| Indoor (evaporator) coil | Corrosion in the thin tubing, often pinholes that take patience to find |
| Outdoor (condenser) coil | Corrosion from weather, salt air, pet urine or garden chemicals |
| Flare and brazed joints | Vibration and age; flare fittings on mini-splits are a common spot |
| Service valves and access ports | Worn valve cores and missing caps |
| Line set | Rubbing against a wall, a bracket or another pipe; damage from yard work |
| Factory defects | Uncommon, and they tend to show early in a system’s life |
What you can safely do
- Note the pattern. Gradual weakening is typical of a leak; sudden failure usually is not. If your AC went from cold to warm overnight, AC blowing warm air is the better guide.
- Look, don’t touch. While the system runs, check the copper lines at the outdoor unit for frost and the visible fittings for oily spots.
- Listen near the outdoor unit and the indoor coil for a hiss, both while the system runs and after it stops.
- Turn it off if there is ice and let it thaw. Running a starved system strains the compressor.
Don’t try to add refrigerant yourself. Refrigerant work requires EPA certification, the charge has to be measured to the specific system, and adding more does nothing to stop the leak.
Turn it off and call when
- There is ice on the copper lines at the outdoor unit or on the indoor coil.
- You hear a loud, steady hiss. If the indoor unit is in a small closed room, open a window or door there too.
- The compressor hums, clicks repeatedly or trips the breaker.
How a leak gets found and fixed
Our EPA-certified technicians first confirm the charge really is low, because airflow problems and dirty coils can look similar on the gauges. Then the search: an electronic detector along coils, joints and valves; bubble solution to pin down a suspected spot; UV dye for a leak that comes and goes; and for leaks too small to find with the system running, recovering the refrigerant and pressurizing the system with nitrogen to watch for a drop.
The repair depends on where the leak is. A valve core or a flare joint is a small job. A damaged section of line set can be replaced. A corroded coil usually means a new coil. After any repair the system is evacuated with a vacuum pump to remove air and moisture, then charged by weight to the manufacturer’s specification, using factory certified parts. You get an itemized price before work begins.
Repair or replace
A leaking fitting on a newer system is almost always worth fixing. The decision gets harder with a leaking coil on an older system, and especially on one that still runs on R-22, which is no longer produced in the US and is costly to recharge. We lay out repair against replacement plainly and without pressure. If replacement makes more sense, AC installation and heat pump services cover the options, and the repair side is on AC repair.
Salt air and outdoor coils
Waterfront homes and houseboats in Sausalito live with salt air, which corrodes outdoor coils, fins and fittings faster than inland air does. Gently rinsing the outdoor coil with a garden hose during the dry season (power off at the disconnect, no pressure washer) helps slow it, and a yearly maintenance visit checks the coil and connections for early corrosion before a pinhole turns into a lost charge.