MCC 50-2104 - System Pump down for Low Side Repair

4-6
© 2015 Mobile Climate Control
T-367 Rev. 05/2015
4.4.2 SYSTEM PUMP DOWN FOR LOW SIDE REPAIR
To service or replace the thermostatic expansion
valves, filter drier, suction line or liquid line solenoid
valve. pump the refrigerant to the condenser and
receiver as follows:
a. Install manifold gauge set to compressor suction
& discharge valve service por ts (items 4 & 3). Refer
to Figure 4-5.
b. Frontseat the filter-drier inlet service valve (9) by
turning clockwise. Disconnect suction pressure
transducer (5) electrical connector, install a jumper
on the compressor mounted low p ressure switch
(2) ( electrical con n ector o n harness).
c. Start the system and run in cooling. Stop the u nit
when suction reaches 0 psig (0 Bar).
d. Disconnect the compressor clutch wire to dis
able clutch operation. Frontseat the compressor
discharge service valve (3) to trap refrigerant in th e
high side of the system between the compressor
discharge service valve and the filter-drier inlet
valve. Wait 5 minutes to verify that system remains
at approximately 0 psig (0 Bar). If system pressure
rises above 0 psig (0 Bar), open the compressor
discharge service valve, re-co n n ect the com
pressor clutch wiring and repeat steps c and d until
the system remains at 0 psig (0 Bar).
e. Service or replace necessary components.
f. Replace filter-drier (11). Leak check con n ections
on the low side of system by adding nitrogen
through t he suction service p ort. Refer to para
graph 4.5.
g. Energize the Liquid Line Solenoid Valve (LSV)
(12) using an external power source (24 VDC) or
magnet fitted t o the LSV stem.
h. Using refrigerant hoses designed for vacuum ser
vice, evacuate and dehydrate the low side o f the
system by con n ecting a vacuum pum p to the cen
ter hose connection of manifold gauge set. Verify
the compressor suction service valve is mid-
seated. Open (backseat) the manifold suction and
discharge service valves. Evacuate system to 500
microns. Close off vacuum pump valve and stop
pump. Wait 5 minutes to verify that vacuum holds.
If vacuum holds below 1000 microns, isolate the
micron gauge from system to prevent exposure to
pressure.
i. Open compressor suction and discharge service
valves and inlet service valve of filter drier.
j. Disconnect external 24 VDC to liquid solenoid
valve (14).
k. Re-connect compressor clutch, low pressure
swit ch and low pressure transducer electrical con
nectors.
l. Run and check refrigerant level. Refer to p ara
graph 4.7.