Powering off autopilot does not always disengage

[Jcat2010]

FYI
The other day I was using the autopilot, trolling in the harbor. When I decided to head into our slip, I powered off the autopilot, rather than put it in standby. I was a bit surprised when after a few seconds the helm began chattering and locked up. Powered back on, out in standby, and everything went back to normal.

 

[watson1987]

By powering off, do you mean powering off the small AP screen? I'm not sure that shuts off the system as the controller/pump and screen are not one component. You can engage/disengage autopilot with just the main MFD without ever turning on the smaller AP screen, my guess is the controller/pump is still receiving signals from the MFD for the course.

 

[Jcat2010]

Yes, I typically use the small AP screen to engage/disengage/set the autopilot. Just never bothered to use the MFD. Apparently the small screen is just a display/IO device. When turned off, it's just the display that's off, autopilot remains on until it receives a disengage/standby input. Garmin said - oops, we never thought about that mode of operation. Not sure of any collateral damage, will test next trip to see.

 

[Ralf H]

Hi there Jcat,

You shouldn't have any collateral damage, as the chatter you heard was the pump reacting to the rudder reaching its limit of travel. This is normal. What's happening is that the autopilot doesn't know that you are in your slip and still wants to maintain the assigned heading. It therefore keeps turning the rudder until it is back on course, which it of course can't do since you're tied to the dock.

The autopilot remains on, even if you turn the small GHC screen off, as the system needs to be available for any other screen that is still turned on. Hope that makes sense.

Cheers,

Ralf