Tracing an electrical fault

Worked Ok for the first season but then the control panel would display " autopilot stopped working" This would only take a power failure for a split second & trip the control. System then needs resetting. It is very dangerous if it turns off & i am below deck & do not realise that I have changed course.

No wiring shows signs of corrosion.

The autopilot is designed for a much larger yacht so I am not overloading it but it happens in rough weather after 2-3 hours & I can sometimes reset immediately & sometimes I leave it for half an hour before it starts again. Then it will fail after a much shorter hour.

I am beginning to suspect a switch because since posting I noticed that one of them seems warm (does have a light in it though) after a while even though rated for 10 amps as per the instructions. Can a switch break down in use temporarily then work again later?

One other problem with autopilots can be under sizing wires so I have ensured that the wires are larger than specified.

Nick & Dave

Thanks for the links on meters

They are not expensive & I will buy both as I quite like analogue & the auto feature on the other is handy

regards

Sam L

A usefull way to aproach these problems is sometimes to eliminate what it isn't. If you rig up an alternative supply and the problem remains then the fault isn't in the supply but in the unit.

"Can a switch break down in use temporarily then work again later?"

All contacts can be intermittant.

"rough weather after 2-3 hours & I can sometimes reset immediately & sometimes I leave it for half an hour before it starts again." it would be handy to know if it was getting power when it doesn't want to restart. (indicator lamp maybe). If it will not reset and there is power to the unit then it's the unit at fault.

You just have to eliminate stuff.

regards Martin

If a switch is suspect, jumper it with a short cable fitted with soldered alligator clips for a while and see if the unit stays on.

Or just change it out with a new switch (with precious metal contacts if possible). Running a new wire from source to unit is also a good idea.

Have you disconnected or unscrewed, then re-connected or re-screwed every termination in the circuit? Have you done the same for all ground connections? This is a fundamental troubleshooting step on vehicles and boats. I've fixed a lot of problems caused just by bad grounds and poor connections (loose or oxidized, needing a re-seating).

Good luck with your troubleshooting.

One further thought - is it possible to power your critical nav equipment with a second dedicated battery close to the nav unit? might be more reliable to do that and charge that battery from the boat supply. Same sort of thinking as using an uninterruptible power supply for a computer.

This is just a thought, maybe the wiring is not compatable with the requirements of the loads applied. I would consider a complete rewire with good size cable and water proof enclosures, new switches etc.. Peace of mind as a hot part of a circuit on a boat is a danger and fire afloat is not good. Permanent connections to equipment to eliminate bad joins, plugs and sockets etc.

Just a thought.

Clive

I would second the idea of a dedicated battery for anything critical. Short leads, few connections, wiring easy to check or replace, just one switch. Fewer components = more reliable.

Steve

I have a pair of AGM domestic batteries 800mm from the electric cupboard with a red flash starter battery.

the AGM's normally sit between 12.8 & 13 V in operation & 14.4V when under charge. I do not believe that they are faulty as they are fairly new & hold the charges for weeks in the winter without topping up the charge. This is the cupboard from where the autopilot wiring starts it then goes down behind ducts & panels to the stern of the boat via a tortuous route !! 90% of the wiring is manufacturer installed-- without any wiring diagrams I might add. I have only installed the AIS, & renewed the compass,  Echo sounder & log & supply to autopilot & log - that is why they kick off from junction boxes & a plotter reserve plug- top right in picture

Edited By Sam Longley 1 on 13/10/2017 20:51:07

Edited By Sam Longley 1 on 13/10/2017 20:55:09

There is enough good advice on equipment needed and what to look for.

May be a bit late but using the half and half tracing method often speeds isolating the faulty half of the circuit then halfway up or back the dead part and so on in ever decreasing halves till - -- -- -- - BINGO !!

Edited By George Clarihew on 13/10/2017 21:20:56

Sam, your photo illustrates exactly why you need to know your enemy before you embark on a fault finding process, most of that wiring will not be involved in the relevant circuit but you need to know what is. As George mentions the half split method is a sound fault finding process but it is essential to know the circuit completely or how do you pick a midpoint? and make meaningful tests.

Mike