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Help! Electric problem..


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Isolator switch is looking more likely isn't it.

 

I recently had a similar failure, in my case I went to start the engine and found all the lights went off when i turned the key to preheat, fortunately I realised pretty quickly it was the switch and replaced it. I took the old one to bits and here are the pictures. if you have these all too common caravan type isolators then these pictures should convince you they are rubbish.

 

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Edited by jonathanA
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Not a Lister expert, so forgive my ignorance. Does your engine have heaters fitted?

We had a similar problem years ago on a previous boat, and couldn't work out what was the cause. The alternator was working fine.

The marine engineer then at Jannel in Burton found it for us with a clamp ammeter.

There was a fault in the ignition switch that meant the engine heaters were on all the time. IIRC the alternator just about kept up with this load while the engine was on, but the batteries were rapidly flattened once it stopped.

Just a thought!

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Not a Lister expert, so forgive my ignorance. Does your engine have heaters fitted?

We had a similar problem years ago on a previous boat, and couldn't work out what was the cause. The alternator was working fine.

The marine engineer then at Jannel in Burton found it for us with a clamp ammeter.

There was a fault in the ignition switch that meant the engine heaters were on all the time. IIRC the alternator just about kept up with this load while the engine was on, but the batteries were rapidly flattened once it stopped.

Just a thought!

Good thought but there are no heaters on a Lister SR2.

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This is a connection problem, it reeks of it. When a connection goes faulty, let's say it puts up a resistance of

5ohms, then as you draw say 1/4A through it you lose 1 1/4V, now try and draw 2A through it you lose 10V. Sometimes a tiny connection remains and drawing any appreciable current simply blows that connection away and it may not re establish until it's wiggled. The symptoms fit exactly. These batteries don't sound flat, they sound disconnected. The split charge relay cutting in when the domestics are loaded is exactly the sort of thing to be expected from a dud -ve and I really doubt there is any fault with the starter.

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Wonder if the isolator melted and went intermittent and took the alt rectifier pack with it sad.png

 

The Blue Seas isolators are s'posed to be good, also the 'TIR' isolators with metal handle seem to be a cut above the ones with the plastic key.

 

cheers, Pete.

~smpt~

Edited by smileypete
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Hi

 

My name is Steve Williams and I am a qualified BSS Examiner and an Electrical Engineer. Having read through your problem and replies, I may have a few pointers for you to check and try.

 

I suspect you have a poor engine earth that may be breaking down with heat AND a wiring error in your charging circuit.

 

Firstly, In the interests of Safety:- Isolate ALL of your batteries from any other items of equipment (Including links to another battery).

 

If you can make a test lamp (or use a car headlamp) with a fairly high wattage bulb (12V x 55w or more) connect it to each of the batteries in turn and leave connected for 60 minutes or so (if your battery is good, then the test lamp will stay bright). If the light fails to light up or goes out after a few minutes then the battery is flat, will require charging fully and then a high resistance drop test to determine if the battery needs to be replaced.

 

Secondly, disconnect the thick cable from your alternator and make up a new one long enough to reach back to the batteries. Then (when you have your starter back) connect one of the batteries to the engine start cables and connect the other end of your new alternator lead directly to the +ve of the battery you are using to start the engine. There should NOT be any load taken from the alternator if the diode pack is ok.

 

Finally, Check that the engine return cable is connected directly to the Negative post of the start battery, that the connections are clean and TIGHT with no evidence of burnt insulation.

 

Now, start the engine. when the engine is running, put a battery Volt Meter across the battery you have used to start the engine, you should get about 13.7 to 14.5 volts.

 

Once you have done this and all is ok, come back to me at the address below or ring me on 07814530679.

 

By the way, how old are your batteries? And it is possible that the starter solenoid on the starter motor stayed engaged when it failed, which would cause the motor to continuously draw current from the batteries. The RCR engineer will identify this if it is the case.

 

Hope this helps.

 

Best of luck

 

Steve Williams

BSS Examiner PIN614

www.iwabss-limited.co.uk

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Hi

As a newbie I can only relate to "old" car issues at the moment.

Dodgy diodes in the alternator pack cause no charging and can also drain the battery with the ignition on.

 

Please don't berate me :P

 

I have only limited knowledge and large words bother me.

 

Alph

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Won't berate you but experience on cars definitely can not be extrapolated straight to boats. By and large cars are wired earth return (the car body being the return wiring) and tend not to use master switches. they certainly do not use master switches in the return circuit (a horrible but all too prevalent practise). They also do not have odd circuits bypassing the master switches and the component's fitted tend to be of a sufficient quality and reliability.

 

Almost all cars are designed and built by true experts, unlike boats where all too often a good carpenter also seems to think he is a good engineer and electrician.

 

What you say may well turn out to be true but on the few symptoms we have been able to glean from the OP it really does sound like a negative (return) fault and given the master switches commonly fitted are well known for causing problems that is the most likely culprit.

 

At present I think there are a number of us here who are wondering why the starter was diagnosed as the fault but as we were not there and hav been given no date on the testing metods and readings we can only wait and see if the OP comes back to use.

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At present I think there are a number of us here who are wondering why the starter was diagnosed as the fault but as we were not there and hav been given no date on the testing metods and readings we can only wait and see if the OP comes back to use.

 

I 'rescued' a boat last year where an RCR guy had diagnosed a faulty starter, started trying to remove it but gave up & walked away with it partly undone (it was a pig to remove & replace!).

There was indeed a starter issue, but it wasn't dead & the real problem was that the starter battery was 8 years old and had decided it had had enough.

 

Tim

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If I've boiled it down to a probable starter motor fault, as a basic test I'll almost always go onto it direct with my OWN jump leads and a known good charged battery to test it. That's if I can get to its terminals of course, but you usually can with maybe a bit of contortionism. To make sure the starter is faulty and once removed I lay it on the ground stick my boot on it and carry out the same test again with my leads and battery to see if it gives a good powerful kick and whizzes up to speed instantly. Never trust other peoples jump leads they're invariably useless and often of the ultra cheap variety with aluminium conductors and naf croc clip connections. My jump leads cost me the grand sum of £15 but that was 46 years ago but they're still going strong, I guard them with my life and I won't lend them to anyone.

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Almost all cars are designed and built by true experts, unlike boats where all too often a good carpenter also seems to think he is a good engineer and electrician.

 

 

I think that sums up a lot of problems on boats. I also knew a lot of electricians who couldn't get their heads round car electrics.

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Connect a known good battery to the starting circuit. Bypass the isolator switch by unbolting the connections and bolting directly together (of course you will need to install a new isolator later).

 

Try starting. I'd place money that your engine will turn over.

 

If the circuit has gone belly up (isolator switch failure either open or closed) then it could be that your alternator 'b' field needs a tickle (or it won't charge batteries once you have your engine running). This involved a sneaky little short across some terminals - if you can work out which alternator you have then I'm sure people here (or me) can give you detailed instructions.

Edited by Alastair
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