Thermo King 919180, Manual

Page: 94 / 148

Refrigeration Maintenance
94
5. Operate the unit on cool, and pump down the
low side to 0 in. (0 kPa) of vacuum.
6. Stop the unit. The condenser and suction
pressures should remain stable, indicating no
leaks.
7. Shift the three-way valve to heat position
using relay board test. Low side gauge will
raise slightly. High side gauge will drop to
approximately 30 to 50 psig (207 to 345 kPa).
Gauges will equalize.
8. Gauges will remain in this position
(approximately 30 to 50 psig [207 to
345 kPa]) if the three-way valve seals
properly toward the condenser and the
condenser pressure bypass check valve seals
properly.
9. Back seat condenser pressure bypass check
valve stem against snap ring. Both gauges
should rise indicating the condenser pressure
bypass check valve is properly releasing
condenser pressure into the discharge tube and
evaporator.
10. Replace the cap on the condenser pressure
bypass check valve.
NOTE: Valve stem MUST be back seated
during normal unit operation.
11. Open the receiver tank return outlet valve,
remove the gauges and return the unit to
normal operation.
1. Check Valve
2. Heating/Defrost Position
3. Cooling Position
Figure 54: Three-way Valve Condenser Pressure
Bypass Check Valve