The following procedure can be used to evaluate the adequacy of the charge level in a vehicle air conditioning system:

1. Operate vehicle at Fast Idle with the A/C on High for 10 minutes;

2. Measure the ambient air temperature: Tamb = _________ºF;

3. Add 33 Fº to Tamb: 33 + Tamb = _________ ºF = Condenser Temperature Index

4. Using the (HFC-134a) refrigerant tables, find the closest pressure corresponding to the Condenser Temperature Index from step 3: Condenser Pressure Index = _______ psig

5. Measure the condenser pressure, psig: Pcon = ________ psig

6. If the Condenser Pressure Index found in Step 4 is within plus or minus 10 psig of the condenser pressure found in step 5 (Pcon), the refrigerant charge level is adequate and no charge need be added or deleted;

7. If the Condenser Pressure Index is more than 10 psig lower than Pcon, the refrigerant charge is too low. Increase the charge by four ounces and repeat Steps 1 through 6 until the Condenser Pressure Index is within plus or minus 10 psig of Pcon;

8. If the Condenser Pressure Index is more than 10 psig higher than Pcon, the refrigerant charge is too high. Decrease the charge by four ounces and repeat Steps 1 through 6 until the Condenser Pressure Index is within plus or minus 10 psig of Pcon.

Return to A/C 101