Three years on we are still getting the occasional Rudder Response Failure. We keep thinking we have a "smoking gun" that we fix and then ... the problems comes back ...
The system was installed installed 2013/2014 and composed of the following components:
- B&G AC42N
- Zeus 7 Touch (the primary device for controlling the A/P)
- Triton and OP10
- RF300 - Wired direct to the AC42N
- Driving a 32,000 lb Stevens 47 monohull
On the long passage
to French Polynesia
we had repeated RRF's - often when changing modes (i.e. Auto to Nav etc). When we arrived in the Marquesas
we called Navico
in the US and did some troubleshooting. On our way from Tonga
to NZ the HLD2000L drive itself died entirely and was replaced by Navico
NZ. Our assumption was that the drive was the culprit especially as the old solenoid had been knocked off during shipping
to us in Mexico.
Last season we headed out with our new drive and still had occasional RRF problems. On advice from Navico we improved some of the wiring
to reduce voltage drops and checked again all the mechanical connections. On the way from Fiji
to NZ the drive stopped working again. This time it was worn brushes
which we replaced.
We have just finished a passage
from NZ to Fiji and we are still getting occasional RRF issues. Some of the times it is during benign conditions and more likely if changing modes ie Wind
to Nav etc. The problem could be "fixed" by waiting some time and resetting. We also turn off the AC42 for a few seconds too but not sure if this is a placebo or not. If we re-engage the A/P and it does not work, you can hear the pump on the drive "whirring" but no sound from the drive itself moving nor any rudder movement. At this point, even though the autopilot is in 'Auto' the helmsman can turn the helm
freely as if the autopilot was in 'standby'. After a few seconds you get the RRF alarm
. At that point we just wait a few more minutes and try again. Eventually the A/P will actually engage as we are back to normal.
Sometimes this occurs when the A/P is working hard such as in a following sea but several times it has occurred in benign conditions when the helmsman is able to drive with minimal helm
inputs and no excessive weather
I cannot recreate the fault at the dock
so troubleshooting is difficult. We do not have easy access to the drive at sea so hard to troubleshoot at sea as one of us needs to drive the boat when the A/P fails.
All mechanical connections seem fine. Brushes
and hyd fluid in the drive are good. No evident corrosion
in any of the fittings.
Voltage drop data summarised below (Test was done at the dock
using NFU with an amp draw of approx 6 amps driving the rudder from full deflection one side to the other):
to AC42N Supply : 0.2 V
- AC42 Supply (at AC42 terminal) to AC42 Drive Output Terminal: 0.15V (i.e. all internal to the AC42 itself)
- AC42 Supply (at AC42 terminal) to AC42 Drive Engage Terminal: 0.58V (i.e. all internal to the AC42 itself)
- AC42 Drive Output Terminal to the drive unit itself: 0.19V (i.e. the voltage drop along the cabling to the drive unit)
- AC42 Drive Engage Terminal to the solenoid itself: 0.22V (i.e. the voltage drop along the cabling to the solenoid or clutch
is as follows and is either IAW the installation
manual or better:
- Power to AC42N: 10 AWG
- AC42 to Drive: 8 AWG
- AC42 to Solenoid (Drive Engage): 14 AWG
- The rudder reference sensor gives all indications of working fine i.e. during and after the RRF the rudder angle is correctly reflected.
- The drive is new and the problem pre-dates this drive.
- Wiring - Last year we moved the positive lead directly to the DC Positive Buss vice the old cct panel to reduce voltage drop. I have just moved the negative lead directly to the battery
to further reduce voltage drop.
- AC42N - Could there be a problem with the AC42 itself ?
- Is the voltage drop from the AC42 Supply terminal to the AC42 Drive Engage terminal of 0.58V excessive or IAW specifications for the device ?
- Could it be overheating
of the solenoid ? Would it help if I mounted a computer fan to cool the solenoid ?
- Based on the noise
heard, my uneducated guess is that the solenoid on the drive is either not operating correctly or, more likely, not getting the correct signal to engage the drive.
It at least works most of the time but as we normally do long'ish passages and at least 4,000 nm a year with a family
onboard it would be sure nice to trust the autopilot.
Any thoughts out there ?