6-18
Modulation Valve Repair or Replacement
Refrigeration System Diagnosis and Service
CSR-20 & CSR-40, September 1999
6.
Place a 1.5 inch wrench on the enclosure tube hex fitting
and loosen enclosure tube one-half turn.
7.
Hold scissors or other thin-pointed instrument in one hand
while you unscrew enclosure tube using other hand. After
approximately five full turns, the enclosure tube threads
should be free of the modulation valve body. Lift enclo-
sure tube slightly and retain valve piston in valve body by
carefully inserting scissors through top return spring
above boss on piston.
8.
Hold valve piston in valve body with scissors while you
finish removing the enclosure tube. Immediately insert
new enclosure tube carefully over piston top. When you
are ready to thread new enclosure tube into valve body,
remove scissors from piston boss and top spring.
NOTE: If the piston is removed from its bottom
seat in the valve body, the entire modulation
valve must be replaced to ensure proper opera-
tion of the modulation valve. Attempting to
reseat the piston in the bottom of the valve body
will damage the bottom return spring and the
valve will no longer operate properly.
9.
Thread new enclosure tube into valve body until it is hand
tight. Then tighten 1/6 turn more with a 1.5 inch wrench.
10. Place new bottom coil housing plate over enclosure tube.
11. Place new coil and coil sleeve on enclosure tube.
12. Place new outer and top coil housing plates over enclo-
sure.
13. Place new o-ring and coil nut on enclosure tube and
torque to 4.1 N.m (3 ft-lb). Plug coil wire harness into unit
wire harness.
14. Pressurize the refrigeration system and check for leaks
(see “Refrigerant Leak Test Procedure” in this chapter).
15. If no leaks are found, recover the refrigerant used for the
leak test (see “Refrigerant Recovery” in this chapter).
16. Evacuate the system (see “Evacuation and Cleanup of the
Refrigeration System” in this chapter).
17. Recharge the unit with R-404A (see “Refrigerant Charge” in
this chapter). Then perform a controller Pretrip Test to
verify system operation and correct feeler bulb installa-
tion.
Modulation Valve Replacement
If the valve body is damaged, replace the entire modulation
valve.
1.
Remove the compressor compartment bracket.
2.
Recover the refrigerant charge from the unit (see
“Refrigerant Recovery” in this chapter).
3.
Disconnect the unit from the three-phase power supply.
4.
Unplug the coil lead wire harness.
5.
Unsolder the compressor side modulation valve joints
from the suction line. Unsolder and remove modulation
valve.
Modulation Valve
1. Top Nut
2. O-ring
3. Coil Housing
4. Coil Sleeve
5. Electric Coil
6. Bottom Plate
7. Enclosure Tube
8. Closing Spring
9. Valve Body
