3111 Coolant recirculation fault.
Sheet 4 Plug 2 Pin-s
This fault is caused by a loss of a 24 volt signal from the control through a pressure switch, float switch, coolant-pump contactor and terminal 437 in the power distribution panel to a 'Digital Input' board in the control.

a) Visually check the coolant level in the sight-glass on the coolant reservoir. Replenish if necessary. Ensure that the clarifier lid is closed and the handle is positioned correctly for the clarifier motor to run. If both the motor and recirculating pump are running continue with paragraph (b), if just the clarifier motor running then the float-switch adjacent to the recirculating pump is open (coolant level low or faulty switch). A temporary link-wire connected between terminals 644 and 645 on TB1 in the PDP will by-pass the switch to test. If neither the motor nor pump are running check overload resets CPC, RPC and CMC in the PDP and refer to paragraph (h).

b) If the same error code persists check for 24 volts at terminals 400 and 437 with a voltmeter (TB1 in the power distribution panel). If there is no 24 volts, indicator-fuse 4 in the PDP may be faulty.

c) If there is 24 volts at 400 but not at 437 either the float-switch or the flow-switch adjacent to the coolant-pump are open, then refer to paragraph (j)

d) If there is 24 volts at both 400 and 437 then the fault lies from terminal 412 through to Plug 2, Pin-s and the 'Digital Input Board' in the control. 

e) Switch-off the control and transpose the 'DI' boards situated in the lower rack to the left. Power-up the machine. If the fault disappears, or a different, unrelated error code shows-up, then the 'DI' board is faulty and a replacement is required. 

f) If the same error code persists switch-off the machine, remove plug 2 and check the continuity from pin-s to terminal 437. There may be a spare wire in the cable loom to utilize if wire 437 appears to be broken.

g) If the wiring is O.K. the fault may be with the 'Watchdog' board (WD 50x) in the control or corruption of the memory. If another control is available the 'Watchdog' boards can be exchanged to test. If the memory is to be reloaded remember to punch-out programme and tool information first (although an up to date back-up tape should always be held).

h) Check for 110 volts AC on terminal 617 (TB1 in the PDP). If there's no voltage present the clarifier safety switches are open or faulty. The switches are located beneath the side cover of the clarifier unit. A temporary link-wire connected between terminals 606 and 617 on TB1 in the PDP will by-pass the switches to test. If there is 110 volts at terminal 617 an overload has tripped-out or is faulty, CPC, RPC or CMC O/L in the PDP. If one has tripped check the associated motor, a pump may be seized or the clarifier brake may need adjustment.

j) Remove the cover of pressure-switch 4 and check for 24 volts on wire no. 449, if 24 volts is present then the float switch is faulty. If there is no voltage at 449, either the pressure-switch is faulty or there is insufficient flow to actuate the switch - the coolant pump filter may be restricted.