FAP-711C Drive Unit Error (June 2019) ..

Britt

New member
My attention was drawn to a earlier post about the FAP-711C Drive Unit Error.
My FAP-711C puts out the same Drive Unit Error every once in a while.

The Furuno AP pilot in my case is used to drive a slim (58 x 13.2 ft) and light weight motor vessel (16 tons with full payload). The ship was launched two years ago in July 2017. We are blue water sailors.

The Furuno AP unit system has been professionally designed and installed by a Furuno dealer.

The FAP-711C (running 6454007-01.24) is directly connected to the FAP-7002 processor unit (running 6454021-01.06). Linked to the processor unit (24V) is a Furuno reversible pump (24V) to drive a 250 cc ram cylinder. The processor unit is linked to the CANbus (12V) as is the heading sensor PG700 fluxgate compass. Part of the system is also a FAP-6112 RRU. Linked to the CANbus is a Furuno GP33 and a Navnet TZTL12F and a DRS4DNXT radar.
All the required FAP-711C init sequences have been successfully executed i.e. dockside setup, ships characteristics, sea trial etc..

The electrical system contains a 525 Amps/ 24V battery system. The main engine is equipped with a second alternator which is set to produce 29V for the first 4 hours. After that it will put out 27V.

The AP system starts up fine (all OKs) and the diagnostic tests show no (potential) problems. The AP does its work flawlessly (in ADV AUTO mode and both in NAV/ECO and NAV/XTE mode) except for the fact that it intermittently puts out a Drive Unit Error. To be more precise.

It generated this error message twice last year (2018) when we were sailing on the North Sea with Beaufort 5,6 on the beam (our maiden trip). I did report the error message to the dealer but he was not able to assist me. He had not seen this error message before.

However, this year the 711C did put out this error message roughly two times a week for the last 4 weeks. I have tried to associate its behavior to rough (weather/wave) conditions and/or to AUTO and/or NAV mode but I found no repeatable pattern. I also looked at the rudder movements but they are not excessive. Also the pump does not get hot. Last week with light winds and following seas and running in ADV AUTO mode the fault happened after half an hour after starting the system.

What I would like to know is how what causes this error message to be put out by the 711C? Is it possible that the unit is experiencing out of bounds conditions (hydraulic pressure, temperature or under/over voltage level?) and only puts out the Drive Unit Error message if the condition count exceeds a preset level? Once I understand by which conditions this error is produced it is probably much easier to remedy this issue.

Your advice is highly appreciated.

Kind regards,
Rob Westermann
 
The error is because the pilot has commanded the rudder/engines to move and they don't move in a timely manner, if at all. Sometimes it does move but it didn't know it did because of the feedback. For those with an RRU, it can be a RRU going bad due to binding/pressure of the RRU arm or water getting inside. It can also be caused by the pump being underrated or it having a problem and not able to move the rudder/engines when under stain. (like fighting waves it can't give anymore than your currently giving). It can be the wiring going to the processor or the pump is too small to carry the needed current. Lastly it can be that someone forgot the bus termination plug on the back of the last control head on either bus A or bus B. I did see one boat with bad Hydraulic get this error. The pilot would command the rudder/engines to move and the hoses would expand before building enough pressure to move the rudder. The delay cause by the poor hoses was enough to delay movement of the rudder where the pilot complained about it. When the pilot says move... it needs to move.
 
Thanks for the swift explanation about this error. That helps a lot.

Since my pump and hydraulic hoses are fairly new and the electric cabling is according to the suggested standard for both the pump and the processor and the bus termination plug has been put in I have concluded that the problem in my system can be caused either by an hydraulic or an RRU issue.

When checked the hydraulic oil level was a little bit on the low side so I added a couple of cc's. I also checked the RRU and greased the mounting points.

We will not sail for a week or two so I will report back my findings thereafter.

Thanks again.
 
We have been sailing for the last three weeks up till the end of July. The first week seemed to go well. No errors. But then -- and it looks to be related to the seastate (more waves produces more errors) -- the error surfaced again. We will be at our home base soon so the next step will be a dock side air bleed of the hydraulics because I suspect that the system (still) has air in it. Will follow up in a couple of weeks. Cheers.
 
Check that your control head(s) have the needed termination on the back also. I have seen that be an issue. It is a common installation mistake.
 
The control head termination is there.

I have air bleeded the pump hydraulics as described in the manual.

Since then we have sailed off an on for the last two months in all kinds of weather and seastates and up till now the error has not surfaced again.

I also had a chat with the dealer who I pointed to this thread. After reading it he suggested to also adapt the rudder gain setting, which I have done as well.

So far so good. I will continue to monitor the AP behaviour of course but for me the issue has been solved, which is a relief.

Cheers,
 
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