Alternator.

[morrisa]

I was replacing one of the batteries on my boat with the engine running and briefly torched the terminals the wrong way round. I blew a couple of fuses but since that incident my battery charging light does not go out complteley, it does dim bit is still visible. Does anyone know if this has damaged something in the alternator? The engine is a Yanmar 4 LHA.

 

[VicS]

You have almost certainly blown the diodes in the rectifier.
Maybe damaged the regulator too ???

Unless you are competent to strip, test and rebuild the alternator I suggest you take it to an automobile electrician who will be able to test it and repair as necessary.

It would have had the same result even without the engine running!

Lucky you did not cause a spark at the battery terminal to ignite the hydrogen gas. Batteries exploding in ones face are not nice!

 

[mil1194]

Slightly OT - can an above average home-user test an alternator even when it is not fitted to an engine. But otherwise agree with ^^^^^ WHS

 

[VicS]

can an above average home-user test an alternator even when it is not fitted to an engine.

You can test the windings for continuity but not for shorted turns.
You can test the rectifier with a suitable meter with a diode test range, (or an old fashioned analogue multimeter with ohms ranges).

Parts like slip rings and brushes you can inspect visually.

With a suitable voltmeter and ammeter and a variable load resistance you can test the whole functioning of the machine including correct operation of the regulator while it is on the engine.

See the article in Practical Boat Owner no 188 August 1982 for some details.
That does describe a Lucas 17ACR but the one fitted to the Yanmar is probably a Hitachi and is probably negative regulated while the ACR is positive regulated.

What do you mean by slightly OT

 

[Tidnock]

You may have popped the alternator without crossing the battery, leaving an engine running and removing the battery is not a good idea, you might be ok with a dynamo

 

[VicS]

You may have popped the alternator without crossing the battery, leaving an engine running and removing the battery is not a good idea, you might be ok with a dynamo

Yes disconnecting the battery from a running alternator could have the same result .. blown rectifier.

 

[Assassin]

One other option is to swap it for a reconditioned unit, it is most likely a Hitachi unit, bot could be a Paris Rhone built unit and rebadged as Yanmars own. Either are common and available off the shelf as service exchange units.

 

[morrisa]

Re.

Thanks for the info.It is a Hitachi LRH180-03C 80amp. I have seen a new one on the internet at £148. Where would I get a rebuilt one, haven't seen any for sale. Not much available where I stay. Link below with some info.
http://ww2.justanswer.com/uploads/heavychevy396/2010-02-04_165632_Delco-Remy_Separate_Regulator.pdf

 

[Assassin]

Try a local auto electrician who repairs alternators, they purchase the components and recondition your unit, their warranty is usually as good as a new unit, and they are much cheaper. Hitachi components are easily and readily available to the auto market as they were fitted to many vehicles, stationary engines, boats, and much more plant and equipment. The alternator is the same, irrespective of its application.