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Old 10-06-2012, 20:23   #1
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Connecting New Autopilot Computer to Old Hydraulics

I'm refitting all the electronics in my boat right now with a full suite of B&G gear including their AC42N autopilot computer. I'm replacing a Robertson/Simrad J300X-40. It's not obvious how the new computer should connect to the hydraulic drive components. The pump itself is only a few years old but I can't quite see the brand/model number the way it is installed. There appears to be an electronic valve that changes the fluid flow to the ram.

The manual is sadly unclear on connecting to an older system.

Old wires are labeled:
- "Pilot Sol-Motor" (obviously sol = solenoid)
- "Pilot Bypass clutch"

New computer has connections labeled
- "Drive" - two posts, no polarity
- "Drive engage" - two posts + and -

My guess is I connect "Sol-Motor" to "Drive", and the other two to each other, but I'd rather not guess. I'm not very familiar with these systems so not even sure if they are even meant to work together.

Any experience/advice here?

Thanks,

JR
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Old 13-06-2012, 10:04   #2
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Re: Connecting new autopilot computer to old hydraulics

Hello jr. spyder,

This is Really Easy. Treat the "Bypass Clutch" wires (+ and -) on your SImrad J-300X-40 as the same port called "Drive Engage" (+ and -) port on the B&G pilot's termination points.

If the pump is only a few years old I would definitely USE it as those Solenoid Hydraulic-Drive units can be very expensive, and they usually last for 15 years or more.

Stay Well or e.mail nme back with questions.

Steve Delany (formerly of Marblehead, MA)
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Old 13-06-2012, 10:31   #3
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Re: Connecting new autopilot computer to old hydraulics

Thanks. I just got the same advice from a B&G rep. Seemed simple, but just didn't want to be sending the wrong current down the wrong wires. Was worth confirming.

JR
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Old 13-06-2012, 10:41   #4
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Re: Connecting new autopilot computer to old hydraulics

Very understandable concern. It's no fun when you "smoke" an electronics component by stumbling forward and guessing...

Shoot me any other questions you may have as I have been in Nav. Electronics for about 16 years.

Steve
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Old 14-06-2012, 03:50   #5
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Just a sec here.

Your old system sounds like it used a solenoid to reverse the drive motion. Hence did you have a constant running pump. The new system looks set up for a reversing pump

Dave
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Old 14-06-2012, 05:46   #6
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Re: Connecting New Autopilot Computer to Old Hydraulics

I've learned all about this now, with the help of the B&G rep (excellent service there so far). I have a reversing pump that will work fine with the new system, and a separate electrical bypass valve in the hydraulic lines. The pump, of course, moves the fluid in either direction. The valve engages/disengages the hydraulic ram from the rest of the system. When the autopilot is disengaged the valve closes such that the fluid in the ram stays in a closed loop in the ram so when you turn the rudder with the wheel you're not also trying to push hydraulic fluid through all the lines and the still pump. Makes a ton of sense once learned and overall a very simple system.
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