Autopilot computer failure

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   Anybody have any first hand experience with the NAC-3 autopilot computer failing while in use? Ours just died while sailing the other night. Got a message “autopilot computer failure” on plotter and the Nav switch on the DC panel blinks when on.

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32mike Members Profile Send Private Message Find Members Posts Add to Buddy List Commadore Joined: 26 March 2020 Location: FLorida, US Status: Offline Points: 453	Post Options Post Reply Quote 32mike Report Post Thanks(0) Quote Reply Topic: Autopilot computer failure Posted: 14 February 2021 at 14:36
	Anybody have any first hand experience with the NAC-3 autopilot computer failing while in use? Ours just died while sailing the other night. Got a message “autopilot computer failure” on plotter and the Nav switch on the DC panel blinks when on.
	Mike S/V Dulces Sueños 458 #087 Tampa, FL

Arcadia Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 27 November 2017 Location: Sag Harbor, USA Status: Offline Points: 1112	Post Options Post Reply Quote Arcadia Report Post Thanks(0) Quote Reply Posted: 14 February 2021 at 17:08
	Sounds like a blown fuse on the dc panel. The display will indicate “failures” when the computer is off line. Be careful when replacing the fuse. It can be tricky. It should be near the connector label XB 4.3
	Leon / ARCADIA 2018 Hanse 588 Sag Harbor, NY

Arcadia Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 27 November 2017 Location: Sag Harbor, USA Status: Offline Points: 1112	Post Options Post Reply Quote Arcadia Report Post Thanks(0) Quote Reply Posted: 14 February 2021 at 17:09
	I should clarify that “failure” would displayed on your Plotter. The DC panel will blink when there is a blown fuse on the corresponding switch.
	Leon / ARCADIA 2018 Hanse 588 Sag Harbor, NY

S&J Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 30 August 2014 Location: Perth WA / Med Status: Offline Points: 1371	Post Options Post Reply Quote S&J Report Post Thanks(0) Quote Reply Posted: 15 February 2021 at 00:04
	I expand on the "tricky" part of fuse replacement, it is best to turn off the 12V DC supply to the control panel when replacing fuses just in case you drop them and they short out something on the panel.
	H458 #159 Primal Mediterranean cruising

Arcadia Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 27 November 2017 Location: Sag Harbor, USA Status: Offline Points: 1112	Post Options Post Reply Quote Arcadia Report Post Thanks(0) Quote Reply Posted: 15 February 2021 at 01:38
	Agreed! You need surgical skill. You may want to upgrade to 20 amp fuse from the factory 15 amp. The dedicated wiring to the autopilot will handle up to 30 amps.
	Leon / ARCADIA 2018 Hanse 588 Sag Harbor, NY

32mike Members Profile Send Private Message Find Members Posts Add to Buddy List Commadore Joined: 26 March 2020 Location: FLorida, US Status: Offline Points: 453	Post Options Post Reply Quote 32mike Report Post Thanks(0) Quote Reply Posted: 17 February 2021 at 11:23
	Thank you gentlemen. I figured it might be a fuse. I’ll see what I can find. I have to admit that the correlation between switches and fuses and wires on that DC panel is a bit bewildering to me. Things don’t seem to match up to where simplicity would dictate they should.
	Mike S/V Dulces Sueños 458 #087 Tampa, FL

32mike Members Profile Send Private Message Find Members Posts Add to Buddy List Commadore Joined: 26 March 2020 Location: FLorida, US Status: Offline Points: 453	Post Options Post Reply Quote 32mike Report Post Thanks(0) Quote Reply Posted: 17 February 2021 at 11:26
	How do you shut off 12 volt DC supply to the panel? Shut off the house battery switch - the red one?
	Mike S/V Dulces Sueños 458 #087 Tampa, FL

Arcadia Members Profile Send Private Message Find Members Posts Add to Buddy List Admiral Joined: 27 November 2017 Location: Sag Harbor, USA Status: Offline Points: 1112	Post Options Post Reply Quote Arcadia Report Post Thanks(0) Quote Reply Posted: 17 February 2021 at 14:18
	Yes. That’s the only way. I can send you a diagram of the DC panel. I’ll need your email (you can private message it to me if you want.
	Leon / ARCADIA 2018 Hanse 588 Sag Harbor, NY

Norman John Members Profile Send Private Message Find Members Posts Add to Buddy List Sub Lieutenant Joined: 07 October 2020 Location: Hayling Island Status: Offline Points: 3	Post Options Post Reply Quote Norman John Report Post Thanks(0) Quote Reply Posted: 17 February 2021 at 17:07
	Just an alternative suggestion - there may be a faulty electrical connection. Dampness entering electrical wires or connectors can cause the wiring to fail - hence no response from the autohelm. Can be worth cutting doing an electrical continuity check or cutting through a wire to check on its state. hope its not your computer. All the best.
	Norman Payne

32mike Members Profile Send Private Message Find Members Posts Add to Buddy List Commadore Joined: 26 March 2020 Location: FLorida, US Status: Offline Points: 453	Post Options Post Reply Quote 32mike Report Post Thanks(0) Quote Reply Posted: 22 February 2021 at 20:38
	As a follow-up, it was a blown fuse. Thanks to Leon on Arcadia I was able to find the right one. The spares kit, however, did not have the small fuses - another trip to West Marine to stock up on various sizes of those. Thanks, everyone for the help.
	Mike S/V Dulces Sueños 458 #087 Tampa, FL



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