Air Conditioning Diagnostic
Step-by-step guide to diagnose a car AC that does not cool: check the fan, compressor, gas level and the most common AC failures.
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First checks
Is the cabin fan working? Does the compressor clutch engage when AC is requested? Is the air slightly cool, warm, or ambient? These three questions split most AC faults.
- No cold air + compressor never engages : often low refrigerant, or electrical fault
- Cools at speed, warm in traffic : fan or condenser blocked
- Ice on the evaporator pipe : low refrigerant or blocked filter
- Weak airflow : cabin filter blocked
- Bad smell : change the cabin filter and clean the evaporator
FAQ
A sealed system should not lose gas. If the AC stops cooling after a year or two, there is usually a leak. Recharging without repairing the leak wastes money.
Only with the correct refrigerant type (R134a or R1234yf), a proper gauge set and the correct weight — overcharging damages the compressor. Leaks must be found and fixed by a professional.
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