Lennox MS8 SERIES Installation And Service Procedures page 85

10. COMPONENT: REVERSING VALVE (HEAT PUMP
ONLY)
DESCRIPTION:
The 4-way reversing valve is a component that switches the
system between cooling and heating modes. By switching
the flow of refrigerant, the heat pump can incorporate the
functions of cooling in summer and heating in winter
together. The 4-way reversing valve consists of main and
pilot valves, and a solenoid coil.
Any of the following starting conditions are required to
actuate the reversing valve for a specific operating
condition.
NOTE — The reversing valve is energized in heating mode.
STARTING CONDITIONS:
1. When entering heating mode on start up.
2. When changing from cooling to heating mode.
3. When entering defrost mode.
4. When entering heating mode after defrost.
TROUBLESHOOTING:
Using a multimeter set to ohms, insert the test lead probes
into the plug end of the reversing valve coil. If resistance
value is between 950 to 1500 ohms then the reversing valve
is good. If not within the specified range, replace reversing
valve.
POWER CONNECTOR FOR REVERSING VALVE (TYPICALLY
PLUGGED INTO THE OUTDOOR CONTROL 4V JACK
Page 85
REVERSING VALVE BODY
REVERSING VALVE 220-240
VOLT COIL
Corp. 1244-L9