Type 2 Linear Drive Not Actuating

[BarefootBoy]

I have a Type 400G Course Computer driving a Type 2 Hydraulic Linear Drive (M81200). Upon pressing "Auto" the clutch engages as evidenced by the wheel locking but the Drive does not steer the boat (even when +/- 10 is pressed). I'm assuming the system is attempting to steer the boat because eventually the "off course" alarm initiates. Since the fluid reservoir is full I suspect something electrical. The voltage out of the course computer "Motor" terminals is ~ 6.5V when +/- 10 is pressed and the same voltage is also being seen at the black & red wires of the pump, but there is no apparent indication that the motor is running. Now for the questions:
1. Is ~ 6.5V an appropriate reading?
2. If so, are there any further tests I can run to verify that pump/motor condition? Can the pump/motor be rebuilt or is a new one needed. What type /model number?
3. If 6.5V is not appropriate is there any troubleshooting that can performed on the Course Computer?

Thank you in advance.

[Chuck - Raymarine - Moderator]

Welcome to the Raymarine Forum BarefootBoy,

Please click here to view a FAQ addressing how to test an autopilot drive unit. Should the drive unit perform as indicated within the referenced FAQ, then the autopilot course computer would be deemed to have suffered a failure. Should the 400G have suffered a failure then then the autopilot course computer, fluxgate, and control head must be replaced with the following autopilot components, as Raymarine's Product Repair Center can no longer service 400G Autopilot Course Computer:
- ACU-400
- EV-1 Sensor Core
- p70 or p70R Autopilot Control Head.

[BarefootBoy]

Thank you for the information Chuck. I'll check the motor with a 12V supply as indicated in the FAQ link but it sounds like the 6.5V coming from the course computer should be more like 12V. I'll post an update with what I find.

[Chuck - Raymarine - Moderator]

You're welcome.

[BarefootBoy]

Chuck:
I determined by following the FAQ directions that the electric motor in the pump is bad. Since I cannot find a motor I guess I'm going to have to replace the pump assembly. Is there any special hydraulic fluid I should use?

On a similar note - I also found out that the voltage out of the course computer is a 0V - 12V pulse-modulated (duty cycle) signal at 19 Hz. When reading the signal with a digital voltmeter one will see the average of the signal at 6V. You have to use an oscilloscope to see the duty cycle.

[Chuck - Raymarine - Moderator]

BarefootBoy,

Please click here to view a FAQ addressing fluids to be used with autopilot hydraulic pumps.