How To Recharge an A/C System Professionally

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If your A/C isn't blowing as cold as it used you, some of your refrigerant has probably leaked out due to a leaky schrader valve in one of the service ports. In this video I will show you how to inject ultraviolet dye into the system to check for leaks, as well as how to use a manifold gauge set and vacuum pump to refill your system with refrigerant.

If there is still refrigerant in your system, you will need to have it evacuated by a shop with a refrigerant recovery machine before you can perform any repairs such as replacing schrader valves or o-rings or any other component.

You can buy UV dye and a UV flash light at any automotive parts store. Remember to use UV protection when using the flash light.

When recharging your system, you should put in the amount of refrigerant that is recommended by the vehicle's manufacturer. There is usually a sticker under the hood telling you how much you need to put in.

In the case where you don't have a sticker, you can go by the pressures displayed on your gauge set. The following chart should help you to figure out the proper pressures for your vehicle:

R134a Pressure-Temperature Chart

Ambient Humidity Low-side High-Side
Temp PSI PSI
70 Low 25 to 30 140 to 190
High 28 to 35 165 to 220
80 Low 26 to 33 150 to 200
High 30 to 36 190 to 260
90 Low 31 to 37 170 to 220
High 37 to 45 210 to 290
100 Low 35 to 44 195 to 245
High 38 to 48 230 to 320
110 Low 40 to 50 235 to 285
High 42 to 52 260 to 350