Author Topic: Occasional voltage drop when using ST4000+ Autopilot  (Read 3157 times)

MarkTheBike

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Occasional voltage drop when using ST4000+ Autopilot
« on: October 05 2014, 01:16 »
Bav 34 / 2001 with a set of ST60 instruments (Tri / Multi / Wind), ST4000+ A/P and Furuno Plotter, all fitted from new. Domestic batteries are 2x140aH, new and fully charged. Sailing Falmouth to Plymouth, nicely balanced so little wheel movement, I suddenly lost a/p pos fix. Couple of seconds later, it came back. Five minutes after that, it went off and stayed off. I put the a/p into STDBY and disengaged the wheel. The pos fix came back. I set the Multi to ENVIRON / VOLTAGE and switched the a/p back on. Randomly, it would momentarily drop  from 12.4v-12.6v down to around 8v and then back up. Back in STDBY, it remained steady at just over 12v. I have DuckDuck'd this and found suggestions about wiring the a/p direct with bigger cable but don't know the size of the existing cable or what size I should go up to. Anybody got any suggestions? Nigel - I saw that you'd had some input in one of the forums a while ago. Do you have any pointers? I should mention that the weather was and had been nice and dry for a long time so I don't think condensation was a problem. I haven't had time to check all the connections (that's on the list) but this was day 3 of a 4 day trip and no problems up to that point.

Thanks all...

(...it was a jolly good sail though, so not all bad...)
ATB

Mark

Nigel

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Re: Occasional voltage drop when using ST4000+ Autopilot
« Reply #1 on: October 06 2014, 07:26 »
If the voltage is dropping during a large current draw, I suggest a bad connection in the part of the circuit that is common to both the autopilot and the GPS. Possibly to the negative busbar.
Nigel Mercier: Forum Administrator

MarkTheBike

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Re: Occasional voltage drop when using ST4000+ Autopilot
« Reply #2 on: October 06 2014, 09:38 »
Thanks, Nigel, that's a good thought. I'll check when I'm down there tomorrow.
ATB

Mark