There are three tubes connected to one side of the main valve body and one tube on the opposite side. The single tube is connected to the compressor discharge line. The center tube on the opposite side is the common suction line to the compressor. The outside tubes are connected to the indoor and outdoor coils.

The pivot valve is responsible for directing the refrigerant flow to the indoor or outdoor coil. There are three small tubes connected to the pilot valve body. The center pilot tube is the common pilot tube and is connected to the center suction line. The outside tubes are connected to each end of the main valve body. The pilot valve consists of a needle valve and spring.

When the solenoid is de-energized, the spring tension closes one pilot port while the other remains open. When the solenoid is energized, the opposite end is closed. The piston in the main valve is pressure operated and will always travel in the direction of the open pilot tube port which provides a path to the center tube. Pressure which will increase in the opposite side of the valve will escape through a bleed port located in each piston. When de-energized, the valve will be in the cooling position.

Figure 42

Reversing Valve

TESTING REVERSING VALVE

Occasionally, the reversing valve may stick in the heating or cooling position or in the mid-position.

When stuck in the mid-position, part of the discharge gas from the compressor is directed back to the suction side, resulting in excessively high suction pressure.

Check the operation of the valve by starting the system and switching the operation from "Cooling" to "Heating" and then back to "Cooling". Do not hammer on valve.

If valve fails to change its position, test the voltage to the valve coil while the system is in the heating cycle. If voltage to coil is satisfactory, replace reversing valve.

Should the valve fail to shift from cooling to heating, block the

air flow through the outdoor coil and allow the discharge pressure to build in the system. Then switch the system from heating to cooling.

If the valve is stuck in the heating position, block the air flow through the indoor coil and allow discharge pressure to build in the system. Then switch the system from heating to cooling.

Should the valve fail to shift in either position after increasing the discharge pressure, replace the valve.

NOTE: When brazing a reversing valve into the system, it is of extreme importance that the temperature of the valve does not exceed 250° F at any time.

Wrap the reversing valve with a large rag saturated with water. "Re-wet" the rag and thoroughly cool the valve after each brazing operation of the four joints involved.

The wet rag around the reversing valve will eliminate conduction of heat to the valve body when brazing the line connection.

SOLENOID COIL (Heat Pump Models Only) (See Figure 42)

The solenoid coil is an electromagnetic type coil mounted on the reversing valve and is energized during the operation of the compressor in the heating cycle.

Should the reversing valve fail to shift during the heating cycle, test the solenoid coil.

TO TEST:

1.Disconnect power to unit.

2.Disconnect coil leads.

3.Attach probes of an ohmmeter to each coil lead and check for continuity.

NOTE: Do not start unit with solenoid coil removed from valve, or do not remove coil after unit is in operation. This will cause the coil to burn out.

Figure 43

Bellows Assembly

Drain Pan Valve

28

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Friedrich racservmn service manual Testing Reversing Valve, Solenoid Coil Heat Pump Models Only See Figure, To Test
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racservmn specifications

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