SOLENOID VALVES AND HOT GAS BY-PASS VALVE

TM 9-4120-425-14&P

SOLENOID VALVES AND HOT GAS BY-PASS VALVE

DIRECT SUPPORT MAINTENANCE REPLACEMENT Continued

0067-00

SOLENOID VALVES AND HOT GAS BY-PASS VALVE

TEST

Equalization Solenoid Valve (3)

NOTE

This is a test for valve operation and the equalization of discharge and suction

refrigerant pressure when compressor is shut off. When compressor is operating,

valve should be energized and closed. This is a normally open valve.

Connect service gauges to service valves and observe pressures with system operating in the "cooling mode"with

unit delivering cold air.

Turn selector switch to "OFF" and observe system refrigerant pressures.

Refrigerant pressures (suction and discharge) should equalize immediately and be at same pressure within 5

seconds.

Remove top rear panel (See WP 0019-00) and operate unit in "cooling mode" with unit delivering cold air for no

more than 2 minutes at a time.

Observe temperature (by touch) of valve outlet tubing.

Tubing temperature at valve outlet should be at approximately room temperature (NOT HOT).

With unit operating as in step 4, and if tubing temperature in step 6 is hot, check solenoid coil by removing the

solenoid coil to feel the magnetic attraction of the coil to the valve.

If there is no magnetic attraction of coil to valve, the problem is electrical and not the solenoid valve.

If observation in step 3 and step 6 are not as stated, solenoid valve is defective and must be replaced.

Liquid Line Solenoid Valve (1)

NOTE

This is a test for valve operation. The valve functions in "cooling mode" to control

cooling output of unit by supplying liquid refrigerant to the cooling coil

Operate the unit in "cooling mode" and observe (evaporator) supply air temperature.

With temperature selector in "coolest" position the supply air temperature should be cold (approximately 15F

below ambient).

With the temperature selector in "warmest" position, the supply air temperature should be same as ambient

temperature or 1 or 2 degrees warmer.

When the unit is operating as in step 2 above, but with supply air temperature not cold, remove top rear panel (See

WP 0019-00) and check solenoid coil by removing the solenoid coil to feel the magnetic attraction of the coil to the

valve.

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