Home › Troubleshooting › Low refrigerant (a leak)
Why is my AC low on refrigerant?
Because it leaked. Refrigerant runs in a sealed loop and is never consumed, so a system that's low has a hole somewhere. Low charge drops the low-side pressure, which makes the evaporator run colder than designed (and ice up), while starving the compressor of the gas flow that normally carries its heat away.
What causes it
A leak somewhere in the sealed loop. Refrigerant is never 'used up' — if you're low, it escaped.
What it does to the cycle
Less refrigerant means the low-side pressure drops, so the evaporator runs colder than designed and can freeze. Meanwhile the compressor runs hot with too little gas flowing through to cool it, and can eventually burn out.
What you'd notice
Warm air, hissing or bubbling sounds, ice on the suction line, and the classic 'it's just not as cold as it used to be.'
What to do about it
- Listen for hissing or bubbling near the refrigerant lines.
- Look for ice on the copper suction line or the indoor coil.
- Check fittings for an oily film — escaping refrigerant carries compressor oil out with it, so oil marks the leak.
- Call a licensed tech. They'll find the leak with dye or an electronic sniffer, repair it, then weigh in an exact charge.
- Refuse a 'top-off' with no leak search. It's money vented into the atmosphere, and it's illegal to knowingly vent refrigerant.
The bottom line
A pro has to find and seal the leak, then recharge to spec. Just 'topping it off' wastes refrigerant and the leak comes back.