SENTRY II 972SM Series, Operation And Maintenance Manual

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Service Instructions
The drive cap assembly contains the drive cap, the main drive gear, drive cap spline, piston
rod and various other parts that should not be dissembled in the field. Visually inspect the
drive cap for damage and free operation of the gear and threaded rod. The only
replaceable part on the drive cap assembly is the O-ring.
Main Piston and Brine Piston - Disassembly and Inspection
Attached to the drive cap assembly is the main piston and the brine piston. The brine piston
(the small diameter one behind the main piston) is removed from the main piston by
unsnapping it from its disassembly latch. To remove the main piston, fully extend the piston
rod and then unsnap the main piston from its latch by pressing on the side with the number.
Chemically clean the piston in dilute sodium bisulfite or vinegar, or replace them. The main
piston is teflon coated. If the teflon coating is damaged, replace the main piston.
Main Piston and Brine Piston - Reassembly
Reattach the main piston to the drive cap assembly. Reattach the brine piston to the main
piston. Reinsert the drive cap assembly and piston into the seal and spacer stack assembly
insert the four screws and tighten the drive cap assembly. Make certain that the main drive
gear still turns freely. Rotate the main drive gear counter-clockwise until it stops ( this action
will ensure that the threaded piston rod will not interfere with the reattachment of the drive
bracket and circuit board assembly.)
Reattach the drive back plate by sliding it over the two
tabs and rotating clockwise until the drive back plate “clicks” into place
Reattach the drive bracket and circuit board assembly to the control valve and connect all
plugs. After completing any valve maintenance, press and hold NEXT and REGEN buttons
for 3 seconds. This resets the electronics and establishes the service piston position. The
display should flash all wording, then flash the software version and then reset the valve to
the service position.
Seal and Spacer Stack Assembly - Disassembly and Inspection
To access the spacer stack assembly remove the drive assembly, drive cap assembly and
piston. The spacer stack assembly can then be pulled straight out. Inspect the black O-
rings and inner seals for wear or damage, replace the entire stack if necessary. Do not
disassemble the stack.
The spacer stack assembly may be chemically cleaned (dilute sodium bisulfite or vinegar)
or wiped with a soft cloth.
Seal and Spacer Stack Assembly - Reassembly
The seal and spacer stack assembly can be pushed into the control valve body bore by
hand. The control valve body bore interior can be lubricated with silicone to allow for easy
insertion of the entire stack.
Reattach the drive cap assembly and piston(s) and the drive assembly.
After completing any valve maintenance, press and hold NEXT and REGEN buttons for 3
seconds. This resets the electronics and establishes the service piston position. The
display should flash all wording, then flash the software version and then reset the valve to
the service position.