Daikin GPHM5 SEER2 M Series Installation Instructions Manual page 16

Troubleshooting the Reversing Valve for Electrical
Failure
1. Place unit into the cooling mode. Test for 24 volts at
the solenoid. If there is no voltage present at coil,
check the control voltage.
2. If voltage is present, loosen the nut on the top of
the coil. Remove the coil, there should be slight
resistance.
3. If the slight resistance is felt, remove the coil. As you
remove the coil listen carefully, an audible click should
be detected. The clicking is due to the movement
of the pilot valve plunger. The absence of a clicking
sound indicates the plunger is stuck.
Troubleshooting Mechanical Failures on a Reversing
Valve by Pressure
1. Troubleshooting the reversing valve can be done by
pressure and touch.
2. Raise the head pressure. In the cooling mode block
the fan exhaust. Once head pressure has been
raised, cycle between cooling and heating and see if
the piston can be freed.
Troubleshooting Mechanical Failures on a Reversing
Valve by Temperature
1. When operating properly the valve contains
refrigerant gases at certain temperatures.
2. The discharge line should be the same temperature
after the valves discharge line.
3. The true suction should be the same as the suction
line after the valve. If there is a 4-degree difference,
valve is leaking
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. An increase
in the suction line temperature through the reversing
valve can also be measured. Check operation of the valve
by starting the system and switching the operation from
COOLING to HEATING cycle.
If the valve fails to change its position, test the voltage
(24V) at the valve coil terminals, while the system is on the
COOLING cycle.
If voltage is registered at the coil, tap the valve body lightly
while switching the system from HEATING to COOLING,
etc. If this fails to cause the valve to switch positions,
remove the coil connector cap and test the continuity of
the reversing valve solenoid coil. If the coil does not test
continuous - replace it. If the coil test continuous and 24
volts is present at the coil terminals, the valve is inoperative
- replace it.
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