A/C H Valve - Diagnosis and Testing Procedures
83chrysler2Models
All Domestic Passenger Car & Truck Equipped With Air Conditioning & C-171 Compressor
Subject
H-Valve Diagnosis & Testing
Index
AIR CONDITIONING
Date
November 7, 1983
No.
24-07-83
P-4169-C
Proper diagnosis and testing of the H-valve is an important factor in resolving air conditioning problems quickly and satisfactorily. The following procedure outlines the easiest, most direct and quickest diagnosis and test.
Before H-valve test is performed a thorough review of the "Safety Precautions" and "Test Procedures" section of the appropriate service manual is highly recommended.
FIGURE 1 - "H" VALVE TEST WITH C-171 COMPRESSOR:
H-VALVE TEST PROCEDURE
1. Install manifold gauge set Figure 1. Test must be made with ambient temperature of 21~ to 27~ C (70~ to 85~ F).
2. A/C System - Close the windows and operate the engine at 1100 rpm passenger car, 800 rpm truck. Set air conditioning controls for "Max A/C", high blower, temperature control lever in full heat position. Electrically by-pass the cycling clutch switch and low pressure cutout switch. Disconnect and plug water valve vacuum hose (gray) Jumper electric cooling fan on vehicles so equipped so that it runs during test.
3. Operate the system for at least five (5) minutes in order to obtain partial stabilization and sufficient heat to load the system. Pressure at the discharge service port should reach 965 to 1655kPag (140-240 PSIG) Figure 1. If head pressure of 965 to 1655kPag (140- 240 PSIG) cannot be obtained, check system charge level (see Systems Charging section)...
4. Extreme care should be exercised in handling freon (see Safety Precautions section). Spray the "H" valve control head with liquid freon (refrigerant) for 10 to 15 seconds. The compressor suction pressure must drop to below -50kPag (15" of vacuum). If the condition is not met, the "H" valve is stuck open and should be replaced. Discontinue spraying with freon and watch the compressor suction pressure. It should increase to a minimum of 262kPag (38 PSIG) and then stabilize at 140-240kPag (20-35 PSIG). Any H-valve which does not produce this response is stuck closed and should be replaced.
Alternate Method
Put crushed dry ice on control head of "H" valve assembly (completely cover head) for a minimum of 30 seconds.
WARNING: ALWAYS WEAR PROTECTIVE GLOVES WHEN HANDLING DRY ICE TO PROTECT HANDS FROM INJURY.
Compressor suction pressure must drop to below -50kPag (15" of vacuum). If the condition is not met the "H" valve is stuck open and should be replaced. Remove dry ice and watch compressor suction pressure; it should increase to a minimum of 262kPag (38 PSIG) and then stabilize at 140-240kPag (20-35 PSIG). Any H-valve which does not produce this response is stuck open and should be replaced.
5. Set engine speed at 1000 rpm passenger car, 800 rpm truck and blower on "Hi". The evaporator suction pressure should be in the range of 138 to 207kPag (20-30 PSIG). If compressor discharge is higher than 1655kPag (240 PSIG), check for restricted discharge line, radiator overheating, air in system, electric fan not operating (if so equipped), or faulty viscous fan drive (if so equipped).
6. If discharge pressure is less than 966kPag (140 PSIG), check compressor gaskets and discharge reeds.
7. Reconnect the electrical wires, water valve, vacuum hose (gray), and set temperature control to "Cool" position.
POLICY: Information only