Alternator Woes Continue

[TwinRudders]

Mornin'
Sadly spent all weekend trying to get alternator working - whilst outside it was sunny and breezy.....

Any suggestions on this:

Basically old alternator rusted out (due to a cooling water pipe spraying water everywhere)

First noticed this - as: 1 - rev counter stopped working (works off alternator) and 2 - when you turned the ignition on - the alarm sounded continuously until you started the engine plus a couple of the warning lights didn't come on. Noticed batteries not topping up. So alternator not working. So...

Did a service exchange on the alternator with C&E - carefully wired it up exactly as before and installed. Went to start engine - no alarm - warning lights light up. Looks better. Start engine. Ignition light (and temperature) stays on plus no revs on the counter. OK so maybe I put the wire for the rev counter on the wrong connector, plus vice versa with the warning circuit... So...

Take alternator off - but all wires where they should be...? Cleaned all connections and re-installed.Same again. Tearing my hair out at this stage!

Any advice anyone please!

Thanks,

Jono

 

[john_morris_uk]

What make alternator and engine please?

 

[pelissima]

Had similar probs last week.
This is what I did.
With enging on (and tacho not working) I checked voltage on alternator, got 14 so OK there. Tacho should have a minus, a plus and a signal line, plus two for a light.
So I checked minus on tacho against a good one. OK
Then I checked the plus on tacho. Oh-Oh NO plus, bingo.
I followed the cable and noticed a multiple plug out of a socket elsewhere.
I put it back and presto.
It might give you ideas.

 

[oldharry]

[ QUOTE ]
Mornin'


Basically old alternator rusted out (due to a cooling water pipe spraying water everywhere)

[/ QUOTE ]

Basically water and electricty do not mix. The water has got in to other connectors, and has corroded them.... leaving you with the lovely job of tracking them all down.

You need a digital volt meter to start with, as it will give a reading whichever way round you connect it, and you are needing to accurately measure voltages down to .1 of a volt.

First, as the whole thing has been sprayed with water and has corroded, the most likely fault is the negative return from the alternator. With the engine running touch the meter probe to the metal frame of the alternator, and the other porbe to the Negative battery terminal. If the reading exceeds .2 volt then you have need to connect the alternator frame directly to the battery negative with a length of heavy wire. Do the same test between the alternator frame and clean metal on the engine block. If the reading is the same as before then the fault is that there is too much rust on the alternator mounts. Your heavy wire could then be taken back simply to the engine. This latter test assumes the alternator is set upo automotive style, with its negative return running via the alternator mounts.

If this does not solve the problem, then you need to check each wire and it's connectors again with the engine running. ease the connectors back so that you can touch the metal of the actual contact on the component you are testing; start the engine, and carefully touch the meter probes to the exposed contacts at each end of the connecting cable. Again any reading over around .2 volts means problems usually in the cconnectirs attached to the cables.

Electricity and water do not mix, and if a lot of water has been sprayed round the engine compartment, then it will almost certainly have caused problems with connectors, and sometimes cleaning them up is simply not enough! But I would firstly suspect the negative return arrangments.

Be very very careful working around a running engine. No loose clothing, tie, or toggles. Anything catching in a moving part or belt can cause instant serious injury - or worse!

 

[TwinRudders]

Hi,

Thanks for your ideas. Couldn't find a fault there.

Got a marine engineer to have a quick look as a favour - and they just said it isn't charging. Basically got a reading of about 12.8v across the neg and pos of the unit with batteries on. Start engine - it should go up to 13-14v - no change. not charging. Defunct. dead. Ex alternator - or that's what I thought...

Anyway took it back - different guy at the shop said immediately - they've given you a 24v alternator. So basicaly I spent all weekend tearing my hair out because they gave me the wrong one.

Next time it will be my first question!

Put the new one on - and I am now very quick at getting them on and off - bingo. 5 min job...took all weekend.

Thanks for suggestions.

Jono

 

[ShipsWoofy]

Interesting, I do not understand why you had no output at all when running though?

It is obviously the reason, I just don't understand it /forums/images/graemlins/grin.gif

 

[snowleopard]

Doesn't make a lot of sense to me either! Unless it meant that there wasn't enough voltage going into the exciter to start it working.

Last time i saw symptoms like that, the engineer took it to his workshop and it was producing 14ish volts but back on the boat - nothing. The end of the story was that a fault in the rectifier was only showing up when under load but working OK on the bench on open circuit and drawing no current. A new rectifier sorted it.

 

[oldharry]

Well thats just rotten bad luck - particularly on a nice weekend like just past!