Tools Required

J 21213-A Four Jack Dual Range Temperature Tester

1. Park the vehicle inside or in a shaded area.
2. Open the doors or the windows to ventilate the interior.
3. Vent the engine exhaust, if necessary.
4. Install high and low side pressure gauges.
5. Record the ambient temperature of the vehicle.
6. Record the relative humidity. Use a psychrometer or consult the local weather bureau.
7. Close the doors and the windows.
8. Set the mode controls to NORM A/C, the blower control on HI, and the temperature control on full COLD.
9. Open the air conditioner outlets.
10. Install J 21213-A or the equivalent into a centrally located air conditioner outlet.
11. Place the transmission in P (Park) or N (Neutral).
12. Start the engine. Stabilize the engine speed at 2000 RPM and start the timer.
13. Run the A/C system until the outlet air reaches the lowest temperature (about 3 minutes).
14. Record the outlet air temperature and the high-side and low-side pressures.
15. Turn the engine off and compare the readings to the Pressure Temperature Relationship of Refrigerant chart and System Performance Test chart. Refer to Refrigerant System Checks and System Performance Test . Correctly operating A/C systems should not exceed these figures.
16. If a malfunction is suspected due to abnormal system pressures, inspect the following:

16.1.

Outer surfaces of the radiator and the condenser cores. Ensure that the air flow is not blocked by dirt, leaves, or other foreign material. Check in between the condenser and the radiator and the outer surfaces

16.2.

Check the evaporator core, the condenser core, the hoses and the tubes for restrictions or kinks.

16.3.

Check for refrigerant leaks. Refer to Refrigerant Leak test or the coach manufacturer's service manual.

16.4.

Check the air ducts for leaks or restrictions. A low air flow rate may indicate a restricted evaporator core. Refer to the coach manufacturer's service manual.

16.5.

Check the compressor clutch for slippage.

16.6.

Check the drive belt for improper tension.

16.7.

Check the accumulator for plugging.

16.8.

Check the expansion tube (orifice) for plugging.

17. If the problem is not found, refer to the diagnostic section in the coach manufacturer's service manual.