ComNav Autopilot

For a few months, I have been experiencing an intermittent problem with my ComNav autopilot. When the pump sits for a while - a few days or more - it "freezes". I can hear the motor engaging but it does not run. A few whacks with a rubber mallet frees it, and then it runs normally. The electric motor is a 12vDC FRACMO (see photo). Any ideas on the issue?

My troubleshooting started by checking the motor brushes. With the brush cap off and brush spring exposed (see close-up of spring), the spring and brush are refusing to come out. For now, I have replaced the cap, wondering how hard I should tug the spring or if there is another intervention?

My comnav system uses an octopus pump, so a bit different. But, a motor is a motor. If the brushes just refuse to come out the slot, they may be cocked in the slot from extreme wear.
You can pull the whole back end of the motor off if everything else fails. Just be mindful of the end caps orientation. Mark with a paint marker or similar.

these pumps do have a life cycle.

My first one died after a few years, the second one is still trucking along some 17 years later.

While the motor may be rebuilt fairly easily, you can find this type of motor/pump assembly readily on ebay or other.

Be sure to size properly for your steering ram. In my case when I replaced the first pump I upgraded to a type 2 pump which drives the ram somewhat faster and easier than the first one.

There is a range that the different pumps are able to serve based upon ram size in cc.

I think you are on the right track with the brushes. It sounds like they are intermittently losing contact due to some combination of wear and accumulated dust. I can't help with specifics about how to take that motor apart, but I'd move to the end cap next. A call to Comnav might help too. Once you get in there, be sure to clean out all the accumulated brush dust along with replacing the brushes.

You might try "burping" the hydraulic oil system and make sure it's full.

Thanks very much for the suggestions. I will "fold" myself into the lazarette this afternoon, take another run at the brushes and if that fails, try to remove the end of the motor (visible in the brush photo). Stay tuned . . . .

I was able to remove the brushes with some rubber mallet tapping and a stronger tug. There is plenty of brush left. I was able to swab out the brush sockets and also polish the contacts on the end of the springs. Smoke test tomorrow (need two people).

Make sure things are cleaned up enough so the brushes move freely in their slots. They depend on the spring to maintain contact with the rotor, and that will be compromised if the brushes can’t move freely.

I have a used, working ComNav autopilot hydraulic pump (needs a belt) for free - just pay the shipping. Let me know - anyone!

FoxtrotCharlie - thank you for the offer but I think I have the issue solved, for now. Smoke tested yesterday and there was no hesitation in the pump motor responding. I used alcohol on the cotton swabs and took a ton of carbon out. Also spent a fair bit of time with 320 grit paper polishing the tabs on the and of the springs; I believe these tabs are also part of the contact system and they are bright and shiny now. Thanks to everyone who chimed in.

If your issues come back don't hesitate to contact Comnav. They have the most impressive customer service I have ever experienced in the marine industry. I bought my boat a few years ago in Fiji. The autopilot wasn't working properly coming, and I was at home trying to help the delivery Capitan diagnose the problem. I downloaded the Comnav PDF of the manual off their web site to figure out where to start. To download the pdf the site made you enter your contact info on a web form. 20 minutes after I download it, an engineer from Comnav called me on my phone. "I saw you just downloaded the manual. Are you having any problems I could help you with?." I could not believe it. He ended up going out to the warehouse and taking pictures of a disassembled rudder position sensor for me so I could see what was inside of it. In the end it must have just been a crusty spot on the rudder position sensor that had been sitting a long time and wasn't making good contact. Just working it back and forth a bunch of times fixed it, and it has been working flawlessly ever since. The guy also followed us a few weeks later to make sure everything was still working well. I could not have been more impressed.

My 34 year old Wagner pump looks exactly like the Comnav pump. Could the parts be interchangeable?

Ancora - the pump motor is a British FRACMO 12vDC motor (FRACMO is still in business). The pump has a ComNav sticker but could be a third-party manufacturer. My guess is that this motor was new in 2001.

Glad you got it working, and it will probably be fine for years to come.

I had a similar failure on a reversing pump years ago and my first reaction was to search for a replacement pump. I couldn't find anything locally, and was going to have to wait a week for a replacement, so decided I had nothing to lose by trying to fix it.

I pulled it apart, cleaned out all the accumulated brush dust, and discovered one of the brush wires had broken at the terminal end. I soldered it back together and the pump ran for years after that. And it took much less time than waiting for a replacement.

Just a follow-up to let you know after a 5-hr (10-hr return) to Friday Harbor last week, the autopilot performed flawlessly. I think swapping out the brush sockets was key. Thanks for all the suggestions.