How to Tell If Your AC Is Low on Refrigerant
How to Tell If Your AC Is Low on Refrigerant
Refrigerant is the lifeblood of your air conditioning system. It's the chemical that absorbs heat from your home's air and releases it outside making your house feel cool. When refrigerant levels are low, your AC can't do its job, regardless of how long it runs.
Here's how to recognize the signs and what to do about it.
How Does Refrigerant Work?
Your AC doesn't "produce" cold air, it removes heat. Refrigerant cycles between the indoor evaporator coil and the outdoor condenser coil. At the indoor coil, it absorbs heat from your home's air and evaporates into a gas. It then travels outside, releases that heat, and returns to liquid form, ready to start again.
When refrigerant levels are low, the system can't absorb enough heat, and your home stays warm no matter how hard the AC works.
One important myth to bust: Refrigerant doesn't "get used up" like fuel. If your system is low on refrigerant, there's a leak somewhere. Recharging without finding and fixing the leak is a temporary band-aid, the level will drop again.
6 Signs Your AC Is Low on Refrigerant
1. Warm or Barely Cool Air from Vents
This is the most obvious symptom. If your AC runs but the air coming out of vents feels tepid — not genuinely cold — low refrigerant is a common culprit.
2. Ice on the Refrigerant Lines or Outdoor Unit
Counterintuitive but true: low refrigerant causes ice to form. Without enough refrigerant, pressure in the system drops, causing the remaining refrigerant to get too cold — cold enough to freeze moisture in the air around the coil or lines.
If you see ice on the copper lines running between your indoor and outdoor unit, or on the outdoor unit itself, shut the system off and call a technician.
3. Hissing or Bubbling Sounds Near the Unit
A refrigerant leak sounds like a hiss (gas escaping under pressure) or a bubbling noise (liquid refrigerant near the leak). If you hear either of these near your indoor air handler or outdoor condenser, it's a clear signal of a leak.
4. Higher-Than-Normal Energy Bills
A system running low on refrigerant works much harder to try to cool your home. The compressor runs longer, draws more electricity, and still falls short on performance. If your bills have spiked without a change in usage, this is one possible cause.
5. The System Runs Constantly but Doesn't Reach the Set Temperature
If your AC runs for hours on end but your house stays at 80°F when the thermostat is set to 74°F, the system doesn't have the capacity to cool effectively — often because of a refrigerant shortage.
6. Humidity Feels High Indoors
Part of what makes an AC feel comfortable is that it removes humidity from your home's air as it cools. A system low on refrigerant loses this dehumidifying ability. If your home feels muggy even with the AC running, it's worth having the refrigerant level checked.
Why You Can't Fix This Yourself
Refrigerant handling is federally regulated. The EPA requires technicians to be Section 608 certified to purchase, handle, and recharge refrigerants. You cannot legally or safely add refrigerant to your system on your own.
More importantly, adding refrigerant without finding the leak doesn't fix anything. A licensed technician will:
Test the system's refrigerant pressure with manifold gauges
Identify the location of any leak
Repair the leak (if possible and cost-effective)
Recharge the system to the correct level
Test performance to confirm the fix worked
What About R-22 Refrigerant?
If your system was installed before 2010, it likely uses R-22 (Freon), which was phased out of production in the U.S. as of January 2020. R-22 is still available on the secondary market but costs $100+ per pound — and supply continues to shrink.
If you have an R-22 system with a refrigerant leak, the economics often favor replacement over repair. A new system using R-410A or the newer R-454B refrigerant will be more efficient, more reliable, and far cheaper to service going forward.
Suspect your AC is low on refrigerant? CSO Mechanical will diagnose the problem, find the leak, and give you a clear recommendation — repair or replace — with no pressure either way.
📞 Call (317) 372-1608 to schedule service. We serve Indianapolis, Carmel, Fishers, Noblesville, Westfield, Avon, Greenwood, and surrounding communities.