WATERAX
MARK-3 Owner's Manual
03/2016
– Page 29 of 52
Digital Overspeed Switch (DOS)
Parts breakdown
ID
ITEM NO
DESCRIPTION
QTY
1 800443
B-6289-3 SCREW M4X0.7X35 PHILLIPS
CHEESE HEAD ZINC
2
2 800400
B-6289-6 LOCKWASHER M4 EXTERNAL
TOOTH ZINC
4
3 700593
B-6289-1 DOS PRODUCTION UNIT
1
4 800402
B-6289-4 SCREW M4X0.7X8 PHILLIPS RAISED
CHEESE ZINC
2
5 800413
B-6289-5 SCREW M4X0.7X8 PHILLIPS FLAT
ZINC
1
6 700616
B-6289-2 DOS MK-3 BRACKET
1
Installation
Install the DOS on the fan cowl. The DOS enclosure serves as the ground. Connect the DOS cable to the
“STOP” tab (far right) on the CDI module.
Troubleshooting
The troubleshooting of the DOS can be done while the
MARK-3 is in operation or by using the DTM DOS Testing
Module (700773).
Below is the normal behavior of the DOS when running on a MARK-3:
DOS LED
Start the engine. The DOS LED shall flash 4 times at engine start up and
shall flash continuously to indicate that the DOS is powered up.
Maximum Engine
Speed Setting
Run the engine at wide open throttle (WOT) and close the nozzle (shut-off). The
DOS shall not shut down the engine.
DOS OFF button
With the engine running, press and hold the OFF button until the engine shuts
down. Engine shall shut down. LED shall flash red and turn off.
Overspeed
condition
With the engine running at WOT, create a loss of prime condition. The engine will
overspeed; the DOS shall immediately shut down the engine. LED shall turn off.
