Should your A/C to suddenly stop blowing cold air, this instructable will help you out. You will need two things:
1. An appropriately sized can of refrigerant. If the A/C system does not have a leak, a standard 20 oz can should do. Most 4 door sedans have a refrigerant capacity between 25 and 35 oz (google your make/model to find the exact capacity) , so if your vehicle is empty of refrigerant, you may need a second can.
Note- For nearly all vehicles after 1995, R-134a is the required refrigerant. Consult your vehicle's manual and double check the sticker under the hood to be sure.
2. A pressure gauge/hose with a trigger. This is usually sold with the refrigerant, but they are reusable and can be attached to other cans of 134a.
Disclaimer- I am not liable for any damage caused to any person or property related to the information contained in this instructable. This is for informational/educational purposes only.
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Step 1: Attach Gauge to Refrigerant Can
The gauge/ hose assembly simply screws on to the top of the can. It has the needle for allowing the freon to flow to the hose. There will be a point in the threading where suddenly it gets tighter- at this point, the needle punctures the can. Try to position your hands to screw the next few threads quickly to minimize leakage from the top of the can. Once the hose is connected, handle the can carefully. The refrigerant can easily cause frostbite on contact with skin.
Step 2: Locate Low Side Port
The low side pressure port for the A/C system is usually located under the hood somewhere above the front right tire of the vehicle. The cap on this port usually indicates whether it is the high side or low side. The ports' connectors are different and won't allow the wrong valve to attach to them, so do not worry about plugging the hose into the wrong one- in fact, the low port is the only one of its kind on the vehicle, so the hose will not connect to anything other than the correct valve.
Take the cap off of the port and start the vehicle, with the A/C on its highest/coldest setting. This procedure will NOT work without the vehicle running and the A/C on high.
Step 3: Prepare R134a Gauge and Connect to Low Port
Adjust the gauge to the range of the ambient temperature outside. The red V formed by the arrows indicates this range. Depending on the ambient temperature, the pressure required to fill the A/C with refrigerant will change. Refer to the back of the can to find the appropriate pressure to fill to based on the ambient temperature. Depending on the weather, it may be necessary to wear gloves. The can gets quite cold as refrigerant is released.
As for the hose, no threading is necessary. The connector simply snaps on to the low pressure port, and is released by pulling the bottom ring upwards. Make sure the car is running with the A/C on maximum before connecting the hose.
When the hose is connected, the black pin might shoot up to a certain pressure, depending on whether or not there is any pressure in the A/C system.
Step 4: Fill Refrigerant
Squeeze the trigger while slowly shaking the can left and right for 3 to 4 seconds at a time. Once released, check the pressure. Do this until the desired pressure is reached. Once filled, pull the bottom ring on the connector and lift up to take the hose off of the low side pressure port. After a few minutes, the A/C should be blowing cold air. If not, there may be a leak in the A/C tubes, in which case a UV dye kit is needed to find the leak.
I hope this helps solve your A/C issue:D Good Luck DIY-ers!