How to Drain & Recharge Your Car's AC Unit

Written by samuel hamilton
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How to Drain & Recharge Your Car's AC Unit
Your car's air conditioning unit provides comfort to the vehicle's passengers. (car heater vent image by robert mobley from

A fully functional air conditioning unit in your car can be the difference between travelling in comfort and suffering in heat. Because vehicle AC units rely on highly pressured refrigerant gasses, even the smallest of leaks can cause the unit to weaken. Because of regulations dictated by the Environmental Protection Agency, only certified mechanics can evacuate and refill your car's AC unit. Draining and recharging your car's AC unit, therefore, requires you to locate an MVAC certified auto mechanic.

Skill level:


  1. 1

    Diagnose the reason you believe your car's AC unit needs to be drained and recharged. If your AC vents are not blowing any air at all, you might need to replace either the AC fuse, the low pressure switch, the fan resistor pack or some element of your AC's wiring. If water is pooling on the interior of your vehicle when you use the AC, you might need to clear or replace the AC's evaporator drain hose. You might also need to replace your evaporator drain hose if the air coming out smells mouldy. If your AC vents are blowing warm air, you will likely need have your AC unit drained and recharged.

  2. 2

    Locate an automotive service technician or repair shop with a MVAC certifiation. An MVAC certification lets a mechanic evacuate and refill air conditioning units in line with Federal guidelines.

  3. 3

    Discuss your options with your mechanic after the problem is diagnosed. Sometimes your AC unit will not need to be fully evacuated and refilled, but simply topped off with new refrigerant. Topping off your unit with refrigerant will only provide a temporary fix, however, because you probably have a slow leak somewhere in the hosing of your AC unit.

Tips and warnings

  • Consult the EPA's "Questions & Answers on Motor Vehicle Air Conditioning" to familiarise yourself with the federal guidelines. The EPA warns of a common practice by auto mechanics to insist on costly procedures based on federal regulations that do not exist or are severely misconstrued.

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