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Old 04-29-2018, 10:43 PM   #1
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Course Setter 21 Auto Pilot

I have a Course Setter 21 auto pilot by Benmar. Thanks to Sam here on the forum I now have an electronic set of manuals.

When I opened the enclosure I found the compass cylinder is filled with a fluid. I think the fluid is suppose to be there but I'm not 100% sure. The manual doesn't say anything about it but it does say that is should be mounted level. So I think the compass needs to float like a regular compass.

I have a theory on how the compass may be providing electronic signals to the auto pilot circuitry but before I dig any further I'm hoping someone can shed some light on this.

Anyone have experience with this model?

There is a little bit more to this story. If you want to read it go to page 9, post 166 of this thread. Prairie 36 Improvements
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Old 05-14-2018, 08:58 AM   #2
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Bringing this to the surface. Hoping to get a reply from someone with experience on these systems. Thanks.
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Old 05-14-2018, 09:06 AM   #3
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You might want to contact Benmar Marine. They still provide service to their autopilots.

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Old 05-14-2018, 10:48 AM   #4
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The fluid dampa the oscillations of the compass card. years ago I refilled mine, i think it was similar. with clear mineral spirits.
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Old 05-14-2018, 09:40 PM   #5
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FWIW Iíve had two boats with this exact autopilot, despite being old they are rock solid reliable. Current boat course setter was dead when I bought it, Benmar repaired it for a very reasonable price.

I think these are 70ís vintage but donít know for sure.
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Old 05-14-2018, 10:11 PM   #6
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I had a courseSetter 21R many boats (and many more years) ago, and ended up rebuilding it myself. As I recall, there are a series (I vaguely recall that there were 60 of them, 6 degrees apart; there may have been more, but the resolution wasn't great) of contacts around the perimeter of a compass. As the compass swings different contacts become active, allowing the "brain" to infer how far the boat had swung off course, and to then adjust accordingly. Pretty basic, but it sure beat hand steering (and made me REALLY appreciate Simrad's modern technology; actually, my happiness from going from hand steering to the CourseSetter was greater than my happiness from going from CourseSetter to really modern -- in terms of sheer course holding functionality, and disregarding all the extra features modern microprocessor based AP's offer, the CourseSetter was at least 90% as good as modern).

Anyway, the problem with my 21R was just that the contacts had become a little dirty. I polished them up and it was good as new. And from what I recall, there was no fluid in mine. I later learned that Benmar would rebuild for a couple hundred $$$, so you might check that out.
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Old 05-15-2018, 07:36 AM   #7
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Thanks everyone. I'm going to clean up the contacts, etc. and see if can get this operating myself. If not, I'll contact Benmar.
I have some Benmar manuals thanks to "SAM" here on the trawler forum.
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Old 07-16-2018, 05:21 AM   #8
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Hi FOG,
I have the Benmar 21R in my PCF40. What I like about it is that is fully repairable at sea... except for the compass unit. The compass has a light sensor and a light. In between is a compass card that has a few black lines to mostly black lines that control the amount of light getting to the sensor based on the course. Looks like a 0.2 to 6v signal (might have been 8v) depending on how much light gets to the light cell. The weakness is in the compass card where the ink tends to fade from the card and no easy way to open and service. I’m in the process of converting it to a digital compass card. Not high on my priority list, but first run of the conversion worked, but was way to sensitive. Next version will have a wider control band to let the direction stabilize. All of the transistors and other parts are off the shelf. I keep spares on board, but since the rebuild, it has worked well. Also, installed a wireless remote that works great from anywhere on the boat. You’ll enjoy working on it. They are tough units built to last. Let me know if you have any questions.
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Old 07-25-2018, 10:53 AM   #9
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Quote:
Originally Posted by Fredribt View Post
Hi FOG,
I have the Benmar 21R in my PCF40. What I like about it is that is fully repairable at sea... except for the compass unit. The compass has a light sensor and a light. In between is a compass card that has a few black lines to mostly black lines that control the amount of light getting to the sensor based on the course. Looks like a 0.2 to 6v signal (might have been 8v) depending on how much light gets to the light cell. The weakness is in the compass card where the ink tends to fade from the card and no easy way to open and service. Iím in the process of converting it to a digital compass card. Not high on my priority list, but first run of the conversion worked, but was way to sensitive. Next version will have a wider control band to let the direction stabilize. All of the transistors and other parts are off the shelf. I keep spares on board, but since the rebuild, it has worked well. Also, installed a wireless remote that works great from anywhere on the boat. Youíll enjoy working on it. They are tough units built to last. Let me know if you have any questions.
Thank you for the great explanation. You have put in a tremendous effort in figuring out the system. It all makes sense to me.
We are doing the Great Loop now and Iíve been busy with other issues, so unfortunately I havenít had a chance to look at my system any further.
Hopefully Iíll get to it before we have to cross a section of the Gulf in Florida this November. Right now some of my tracks look as though Iíve been tacking a sailboat. Lol
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Old 07-25-2018, 11:25 AM   #10
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FOG,


I was having a similar issue and after troubleshooting the problem for a while it seems to have settled down. I suspect that it was either caused by some air bubbles in the oil that was getting in the way of the light sensor or the mechanical cable that runs from the helm down to the compass unit was sticky. When I get a chance my plan is to disassemble the mechanical cable and give it a good cleaning and grease it.
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