Home › AC Refrigerant › Common refrigerant problems
Start with the symptom you actually have. Each row tells you what it usually means, what else causes exactly the same thing, and what to check before you accept a refrigerant diagnosis.
That second column is the point of this page. Low refrigerant and restricted airflow produce nearly identical symptoms, and one of them is a $20 filter.
| What you notice | Usually means | But could also be | What to do first |
|---|---|---|---|
| Air is cool but not cold | Low charge, or restricted airflow | Dirty filter · blocked vents · dirty coils · failing blower | Check the filter first. It is free and it is the most common cause. |
| Ice on the copper line or indoor coil | Low charge, or restricted airflow | Dirty filter · closed registers · dirty evaporator coil | Turn the system to fan-only to thaw it, then check the filter. If it re-freezes with a clean filter, get it diagnosed. |
| System runs constantly, never reaches setpoint | Low charge, undersized system, or dirty condenser | Extreme heat · dirty outdoor coil · duct leakage | Rinse the outdoor coil with the power off. If it persists, it needs measurement. |
| Hissing or bubbling near the indoor unit | Possible leak, or normal metering-device flow | Normal operation at the expansion valve | Worth mentioning to a technician, not an emergency on its own. |
| Oily residue on line-set joints or coils | Very likely a leak — refrigerant carries oil | Rare: an old service connection | This is one of the better leak indicators. Point it out; it narrows the search. |
| Faint sweet or chemical smell near the unit | Possible leak | Mould in the drain pan · electrical odour (different problem) | A persistent chemical smell is worth a call. An electrical burning smell means shut it off. |
| Needed refrigerant again this year | An unrepaired leak | Nothing benign — this is not normal | Ask what leak search was performed and what it found. This is the pattern worth pushing on. |
| Quoted a large recharge on an old system | Real leak plus aged equipment | R-22 systems make this expensive fast | Get the repair-versus-replace numbers before approving. |
The five questions people actually arrive with
“My technician says I’m low on refrigerant. Is that normal?”
Being low is not normal. Refrigerant circulates in a sealed loop and is not consumed, so a meaningful shortfall means it leaked, was never fully charged, or was lost during a repair. Any of those has an explanation worth hearing. Why refrigerant does not run out.
“How much should a recharge cost?”
Typically $200–$600 for an R-410A system, and $500–$2,000 for R-22, where every pound is reclaimed stock. Run your quote through the checker.
“Is the amount they added a lot?”
Depends entirely on your system’s total. Two pounds into a 3-ton system is meaningful; two pounds into a 5-ton system is less so. Convert it to a percentage.
“Do I have to replace my system because of the refrigerant rules?”
No. The EPA restricts what manufacturers may build, not what you may keep. R-410A systems remain legal to own, service, and recharge. What the AIM Act actually does.
“Should I fix it or replace it?”
Check warranty first — evaporator coils frequently carry a 10-year parts warranty, and that one fact moves more quotes than any negotiation. Then compare repair against replacement with real numbers. Work through it here.
What you can safely check yourself
- The air filter. First, always, and it costs nothing to rule out.
- Supply and return vents. Blocked or closed registers starve airflow.
- The outdoor coil. Power off at the disconnect, then rinse gently with a hose — never a pressure washer.
- Oily stains on line-set joints or coil surfaces. Photograph anything you find; it genuinely helps the technician.
Everything past that needs gauges on a sealed pressurised circuit, which requires EPA Section 608 certification.
Where this site stops
We will help you understand your equipment, read your invoice, and ask better questions. We will not tell you how to buy refrigerant, connect gauges, or charge a system. Opening a sealed refrigerant circuit requires EPA Section 608 certification under federal law, and there is no homeowner exemption. Venting refrigerant is separately illegal. This is genuinely a licensed-technician job, and the reason is legal as much as technical.
Related: Refrigerant hub · 20 questions to ask · AC not cooling · Frozen evaporator coil · Find an HVAC pro
Frequently asked questions
What are the symptoms of low refrigerant?
Cool but not cold air, longer run times, ice on the copper suction line or indoor coil, hissing, oily residue at line-set joints, and rising electricity bills. Restricted airflow from a clogged filter produces almost the same symptom set, so check the filter before accepting a refrigerant diagnosis.
Why does my AC need refrigerant every year?
It should not. A sealed system holds its charge. Needing refrigerant annually means there is an unrepaired leak — ask what leak search was performed and what it found.
Can a dirty air filter cause ice on my AC line?
Yes, and it commonly does. A clogged filter restricts airflow across the indoor coil, dropping its temperature below freezing so condensation freezes instead of draining. It looks identical to low refrigerant and costs a fraction to fix.
What does a refrigerant leak smell like?
Most residential refrigerants are close to odourless. Some people report a faint sweet or chloroform-like smell near a significant leak. A sharp electrical or burning smell is a different problem — shut the system off and call someone.
Sources & verification
✓ Verified against a manufacturer, regulator, or standards source
- EPA, “Homeowners and Consumers: Frequently Asked Questions” (HCFC phaseout) — epa.gov
⚠ Provisional — market-survey estimate, not a manufacturer or regulator citation
- Cost ranges are aggregated from HVAC cost-guide market surveys, collected 2026-08-31. They are not manufacturer or regulator figures, and regional pricing varies widely.
Last reviewed 2026-08-31. How we verify what we publish →
