Misfiring Watermota crossflow.

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Re: Misfiring Watermota crossflow.

Post by JIML on Wed Aug 15, 2018 9:44 pm

If you have an alternator, check the small wire on the back of the alternator is connected.  Also check the bulb and that 12V is being supplied to the bulb.  Most alternators on our boats need to be excited to produce current, this excitation is supplied by the warning light circuit.  If the bulb is blown or the lead has become detached - then you will have no light and the alternator will not produce current.

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Re: Misfiring Watermota crossflow.

Post by F23 flittermouse on Thu Aug 16, 2018 7:43 am

Stephen, no ignition light is probably a fault in just that, as M says, it's usual for the ignition light to come on when the key is turned and go OFF when charging.
It could be something as simple as a loose or bad connection in the lamp unit, a sharp tap will often bring it back to life ! Mine has done that in the past and the simple remedy has sorted it, hopefully yours ditto !!

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Re: Misfiring Watermota crossflow.

Post by Stephen on Thu Aug 16, 2018 11:28 am

JIML - You're explaining that an alternator requires an initialising current via the warning lamp circuit, and once generating no longer takes the current from the lamp circuit.  You gave me the clue to research it further and it seems the current is actually reversed - pushes back - to the point that the lamp gently extinguishes! I never knew! Full exposition here:-  

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I hope it is as simple as changing a bulb: I expect to have to grope under the alternator. My fear is I blew a diode (See Surge Quench Diode note) because when I was having engine trouble I switched the charging, with engine running, between batteries via the changeover switch without hesitation when even that can be the moment of death - instantaneous soaring voltage - for an alternator set-up if that protecting diode, if fitted, had ever previously been sacrificed. Groan ....

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Re: Misfiring Watermota crossflow.

Post by Minerva on Thu Aug 16, 2018 11:36 am

current only travels from one high voltage to a lower one. Its the fact that the rotating dynamo/alternator generates an emf (voltage) that feeds onto the  previously 0 V end of the bulb that means there is no longer a voltage across the bulb and hence no current flows through it once the generator up and running. A blown diode would affect overcharging but not necessarily affect the ignition light. I say not necessarily because I would need to examine the cct diagram to be sure.

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Re: Misfiring Watermota crossflow.

Post by BotleyBouy on Thu Aug 16, 2018 9:18 pm

If you do need to replace the lamp do not use an LED because the current won't excite the alternator.

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Re: Misfiring Watermota crossflow.

Post by Minerva on Fri Aug 17, 2018 12:19 am

L
Hi ...bit late for this but I don’t get this tickling the alternator stuff. An alternator works by having fixed DC current stator and a multicoil rotor that operates to slip rings rather than commutator to provide an AC output that is then converted to DC via a diode bridge. There’s no tickling AFAIK (although I confess to not understanding the meaning of tickling in this context) and the warning light function is not a dependency of the alternator function. Sorry BB but don’t agree.

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Re: Misfiring Watermota crossflow.

Post by Stephen on Fri Aug 17, 2018 3:33 am

Have you been reading the info in my link earlier? I'm no technician and its all new to me but I found it all a model of clarity. Machine sensing and Battery sensing and the maintenance of the wiring as a normal routine I found easy to understand and regarding optimum battery charging success it explained a lot. Because I have a friend with a narrowboat I was familiar with the reference to (optional) advanced Voltage Controller/Regulator which few cruisers such as ours would likely have with our limited power needs/no inverter or washing machine. 
I noticed too that the article had a reference to what a diligent BSS inspector could be looking out for. All relevant and I hope the whole thing all correct?

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Re: Misfiring Watermota crossflow.

Post by BotleyBouy on Fri Aug 17, 2018 7:58 am

Have a read of this http://arrc.ebscohost.com/ebsco_static/repair-tips/8852CH12_The_Warning_Indicator_Light_or_.htm and this https://www.howacarworks.com/ignition-system/troubleshooting-the-ignition-warning-light which also covers a dynamo system.

The LED issue is well know in the classic car world. It's an easy thing to check.

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Re: Misfiring Watermota crossflow.

Post by F23 flittermouse on Fri Aug 17, 2018 9:15 am

Minerva, the ignition light function is to 'excite' the windings, if no ignition light when switched on then no charging will start.
Stephen, if your diodes are blown you would know about it from the smell !! Fried electronics !! Don't ask !!

It's relatively easy to replace the diodes they come as a unit, l also changed the rectifier while l was at it. There are kits on eBay

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Re: Misfiring Watermota crossflow.

Post by Minerva on Fri Aug 17, 2018 10:15 am

Ok guys...I will need to come back to this one. I am interested in electrics and studied it years ago ...but I confess I didn’t read the links and I need to focus now on boat prep for the tidal challenge. This will bug me now! I am one of those people that needs a circuit diagram to understand it. I will read the links later if I survive the tidal! Cheers

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Re: Misfiring Watermota crossflow.

Post by Stephen on Fri Aug 17, 2018 10:54 am

A wonderful forum this, driving both body AND mind to greater things! Great good luck with the tidal challenge and don't forget the 30 metres!

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Re: Misfiring Watermota crossflow.

Post by F23 flittermouse on Fri Aug 17, 2018 12:26 pm

[You must be registered and logged in to see this link.] wrote:Ok guys... if I survive the tidal! Cheers
You're in the best company so you will be fine !  Good challenge, only wish I was 20 years younger, or 10 would do !
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