Autohelm
AutohelmAutohelm
Autohelm
SeaTalk Service Manual
8
4. Type'0'Piston Pump (Z081)
A faulty type '0' pump should be replaced as a complete item. Care should be taken
when removing the pump, not to introduce any dirt into the hydraulic system.
The type '0' pump is sensitive to trapped air and care should be taken to remove it
during installation and commissioning.
4.1 Type '0' Pump Reinstallation
When a faulty pump is replaced new sealing washers should always be installed
between the fittings and the pump body. Connect the reservoir line to the pump
leaving the two drive pipes disconnected at points A and B (Fig.3). Temporarily blank
off the two tee unions to the steering system to avoid fluid loss. The pump should
then be bled using the following procedures:-
1. Fill pipe B with oil.
2. Connect pump drive cable to a 12V dc supply via a 10 ohm 50W resistor. This
allows the pump to rotate slowly without cavitating.
3. Continue adding oil to pipe B as the level drops. Note: If oil is expelled from pipe B
then reverse the connections to the pump.
4. Stop the pump when oil appears out of pipe A. Reconnect A to the steering system
and repeat steps 2 and 3 until the steering ram moves.
5. Observe the movement of the ram and turn the helm pump in the opposite
direction to keep the rudder stationary. This will cause any remaining air in pipe A to
be drawn up to the helm pump and vented.
6. When all the air in pipe A is cleared stop the pump and reconnect pipe B to the
steering system.
7. Reverse the polarity of the pump and repeat from section 5.
Note: This type of positive displacement pump is sensitive to trapped air. It should be
thoroughly bled before using the autopilot.
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