alternator HELP!

[paulcooper]

I decided to re-route the wiring loom on my Perkins 3 cy diesel to avoid the hot spots. Now I come to reconnect the alternator I find that the loom has a blue and a white wire but the alernator has two blue wires which I did not notice as they were covered in paint.

I am assuming that these wires are polarity sensitive? How can I check which way to connect? I have a small multimeter so can do some basic testing. Oh the alternator feeds into a regulator which is a solid state type with a heat sink with fins.

Can some "expert" help me with this one.

All solutions gratefully received.

Paul

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[halcyon]

A few question to start,
you say you have two blue wires on the alternator, how did you seperate it from the loom when you started?
Were are the two blue wires on the alternator ?
You can try turning on the ingnition switch, and see if you have a voltage down one, or both ?.
Have you located the main pos and neg (?) cables ?
Have you a rev counter powered of the alternator ?.


Brian




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[paulcooper]

Hello Brian,

Thanks for the quick reply.

On the alternator there are two blue wires coming out from the insides, they are the only wires visible. They were connected to the wires coming from the regulator
by two bullet connectors. I did not take note of the correct way round as I expected the same colours to be on the alternator but found when I scraped the paint off to reconnect that this was not so, I dont want to connect up wrongly and spoil the alternator or the regulator.

There is no rev counter fitted or wiring for this.

Thanks,

Paul.



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[halcyon]

Are they small wires?
Is it a stnadard regulator, or a add on, ie adverc / stirling ?

Brian

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[Heckler]

sounds like an addon, like when we solder wires to the brushes as per sterling.
stu

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[Alex_Blackwood]

One wire will be the sensing wire from the alternator the other will be the feed to the alternator field windings from the regulator. If you put your multimeter (set on ohms) across the wires from the regulator you should only get a reading in one direction. When you get the reading the wire connected to the positive side of the multimeter should be the one going to the alternator field.
If you can find the warning light wire on the alternator and go between that and the ends of the two wires from the alternator one should have a slightly higher resistance than the other. That is the field wire from the alternator.
The above is according to the diagram I have and without seeing your set up I cannot guarrantee it. Anyway hope it is of some help.
I don't want to sound critical as you experience is not funny but if anyone reading this can take note, the first rule in disconnecting ANYTHING is MARK IT.

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[paulcooper]

Thank you Alex,

The information that you have given should enable me to re-connect the wires with a little more confidence. Yes I know I should have marked them and usually do but Murphys law says the first time you dont is the one you should have.

The regulator is nothing special as was suggested adverc/sterling ? It was the original one fitted about six years ago when the boat was re-engined. There are only the two wires between the alternator and the regulator but if they were wrongly connected I have been informed I could ruin both items.

I will be going down to the boat at Hayling Island tomorrow to re-connect and you should hear me swearing if I get it wrong, Wherever you are.

Thanks to all Paul.

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[William_H]

A word of warning here on multimeters. A digital multimeter will present a positive voltage on the red lead while a old moving coil analogue meter will present a negative voltage on the red lead (usually) perhaps you should be specific about a digital multimeter maybe moving coil types are dynasaurs anyway. I would have expected the output wir of the alternator to be quite heavy compared to the field coil wire and usually there are bolt terminals unless as has been suggested wires direct to the internals have been added. regards ole will

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[VicS]

Also digital multimeters will not always, if ever, give a reading in the forward direction for a diode so if the meter has a diode test range then one should use that instead of the resistance ranges.

In the case in point I think the two wires in question are the connections between alternator and regulator, presumably the output connection is obvious and has been identified without any doubts. There must also be an earth (-ve) connection beween the two and there must also be a connection to the warnimg light but this maybe on the regulator rather than the on the alternator.

Once the wires on the regulator are identified from the manufacturers literature or helpline perhaps the field connection on the alternator can be identified as it will go drectly to one of the brushes. It will also register as practically zero Ohms to earth irrespective of polarity.

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[halcyon]

Could be a gamble, the regulator appears to be standard, but if fitted 6 years ago seems odd. The two wires could be two feild control, or they could be a field supply to regulator for warning light, and the second one to earth the rotor via regulator. Depends if it's a positive or negative field control.
Would help if the make of alternator and regulator were known.

Brian

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[paulcooper]

Now you are getting me all confused.

There is no earth wire on the alternator so I assume that it is earthed via the chassis to the engine bracket.

The two wires coming from the alternator are both the same size.

There is no makers name on the alternator but it is quiet small (about the size of a small tin of beans) perhaps a bit bigger and has no external connections just the two wires coming out in a sleeve from the inside.

Also there is no ident on the regulator but this is about 4" x 2" with black cooling fins on the top and this unit is bolted to the metal instrument panel I assume for transfer of heat?

My test meter is a small digital ( about £10 from Maplin).

Where do I go from here?

Paul.

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[halcyon]

Are there only two wire to the black finned unit?
You must have at least a wire to the battery ?
Finned unit could be a rectifier.

Brian

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[VicS]

This is beginning to sound like a very small alternator with a permanent magnet field feeding AC to an external rectifier with some form of shunt regulator. It would explain why there are two identically coloured wires but is such a thing likely?

More information on the connections on the finned component might help.

Is there any continuity between the wires themselves or between them and the chassis.

If the thing is run up to speed without being connected up what do you get out AC or DC and between what and what, Or nothing at all.

This is more of a puzzle than the time I first met an alternator with no brushes, slip rings or magnets (Oh yes there is) until I saw it all in bits.

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[andyball]

Well it doesn't sound like a std. car style alternator (rather small...just two wires from it, both same size, no "bolt on" connection)

Has the black finned unit got a connection to the battery?...any other connections?

You could have a permanent magnet alternator (tho' haven't seen many on boats), in which case the two small wires can go either way around, but tell us what wires the "regulator" has got & it should be possible to tell you how to check with your meter.

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[paulcooper]

Thank you VicS,

Been to the boat today and after some testing found that you were correct it is a permanent magnet alternator giving out AC into the regulator which I assume rectifies the voltage to DC. All connected up and charging OK.

Thanks to all who contributed and long live the Forum..

Happy sailing,

Paul

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[VicS]

Re: Nice to be right

Thanks for reporting back. It's jolly nice to be right once in a while!

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[Alex_Blackwood]

Agree with VICS, thanks for feed back. Even those of us who jumped in with feet and mouth have learned.
EVERY DAY IS A SCHOOL DAY!

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[William_H]

Re: Nice to be right

Hello VicS Just cos I like rattling on you mentioned brushless alternators. They are a brilliant idea virtually all largt jets use them. I am not sure about new B747 jumbos but the originals had 6 alternators at 40 KVA ( kilowatts) each. one on each engine and 2 on the auxilliary power unit. All are 115 vac 400 cycles per sec 3 phase generators driven by a constant speed drive a bit like a car automatic gearbox in reverse so that alternator runs at constant speed regardfless of engine revs.
Any way the field coil (the rotating magnetic source)( in our boat altetrnators fed DC via brushes) is fed by a small alternator with the generating coilss and rectifiers built onto the same shaft. The field coil for this small generator is around the outside (fixed) so that varying the DC current through the outside field coil generates current in the rotating coil which then feeds via rectifiers the rotating field coil of the main alternator which induces a large current in the generating coils fixed around the outside. The only wearing parts are the bearings a brilliant idea I wonder when we see them on cars and boats

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[andyball]

brushless alternators

you can already buy brushless alternators for cars & boats....also remember working on m/c's with them from late 70's.

Think <A target="_blank" HREF=http://www.electrodyne.com/about.html>electrodyne</A> (& others?) do them, with option of remote fan-cooled rectifier pack.

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[Askival]

I have purchased the Sterling pro digital regulator and remote control, I have soldered two wires to the alternator as stated in the installation guide, (this is to identify the field wire) one wire reads 14 volts the other wire reads 0 volts. I took the alternator to an auto spark and the alternator is working OK, he also stated that the voltage readings where what they should be 14 & 0. I cannot get reading 2-10 volts from either of the wires as per the Sterling installation guide. The only terminal on the alternator that gives a voltage of 7 volts is a spade terminal with a purple lead apparently for a tachometer, has anyone installed this regulator and had the same problems?. The alternator is a Valeo 35 amp and is new.



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