Refrigeration Service Operations (Rev 1/99)
65
NOTE: This orifice may become plugged with dirt
unless the refrigeration hose and solenoid valve are
kept clean.
Engine Compressor
Installation
1. Install the metering orifice on the suction hose fitting.
2. Connect the refrigeration hose to the metering orifice
fitting.
3. Open the refrigeration valves.
Testing the Liquid Injection Solenoid
Valve and Metering Orifice
1. Disconnect the LIS wire from the liquid injection sole-
noid.
2. Install a gauge manifold set on the engine-driven com-
pressor.
1. Liquid Injection Metering Orifice
3. Set the thermostat on the lowest setting.
4. Start the truck and run the unit on the engine-driven
compressor until the suction pressure stabilizes.
5. Place a jumper wire between CH and the LIS terminal
on the liquid injection solenoid.
6. With the jumper wire in place the suction pressure
should rise.
7. With the jumper wire removed the suction pressure
should return to the stabilized pressure in step 4.
8. If the suction pressure does not change, check the CLU
wire for voltage, the liquid injection solenoid valve, or
the metering orifice.
9. Shut off the unit and the truck, remove the gauge mani-
fold set and replace the LIS wire.
CHECK VALVE REPAIR (Model 20 Only)
Testing the Check Valve
The check valve is a very important part of the Model 20
system. The check valve isolates the engine-driven com-
pressor from the electric standby compressor, ensuring the
compressor oil and refrigerant do not migrate between com-
pressors. The check valve should be tested when the system
is initially charged and operating and anytime the system
has been opened for service or repair. Testing the check
valve requires two gauge manifold sets.
1. Disconnect the liquid injection solenoid valve wires.
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