Alternator suddently not putting out voltage... help!

[Dr Bob]

Ivan, you didnt answer if it is a Beta 43.

If it is then seriously, look at the wiring loom connectors. I am not sure if the alternator field wire goes that way but when pootling along last year the rev counter stopped working and then when I moored up the engine wouldnt stop. It happens frequently on these engines. Pull the plug apart, clean the terminals and put back together tensioned with plastic tie wraps.

[nicknorman]

25 minutes ago, ivan&alice said:

I have never had a working set of engine lights. I was indeed cleaning around the engine wiring - the wires had all been  wrapped a generation ago with black electrical tape which had melted into a gooey mess. Someday I'd like to fix all that but it isn't a priority at the moment. I definitely did a lot of tugging and pulling but not since this morning, when everything was working as it should. And I'm fairly sure the alternator wires are OK.

 

The alternator has three terminals but only two cables - a thick red one (25mm^2 ish) and a teeny green and yellow one (2mm^2 ish).. I'm guessing its negative is the engine block, since I can't understand how a current could be that asymmetric.

 

Tomorrow I'll use a meter to test that both cables are intact. Not sure what else to try.

As you suspect the thick red is the main positive output and the negative return is via the engine block / alternator case. The teeny green and yellow one is probably the initial excitation for the alternator, normally from the ignition switch via the warning light. But I suppose it could be the feed to the rev counter. Remind us, do you have just the one alternator and is there a working rev counter / tachometer? Any markings on the case by the green/yellow wire terminal? Might be W or D+

[jetzi]

1 hour ago, Mike the Boilerman said:

I've an idea that might have just changed!

Not sure what im missing that would help too much, i can stick my arm in the engine bay and get a current reading. It's a nice to have for sure, but there are so many more important things to fix!

 

No I don't have a rev counter nor any engine lights whatsoever. I did measure the current going into the glow plugs and those are definitely working. But the rest of the wiring in the engine is a bit of a mess.

 

1 hour ago, Mike the Boilerman said:

A photo of the back of the alternator would be really good now.

Full disclosure - I stole a cable from the alternator yesterday to link to my BMV shunt. It went from the alternator to a positive stud that had only a long cable to the battery, so I linked that cable directly to the alternator.

 

In doing so I managed to loosen the terminal that comes out of the alternator. I thought I'd broken it completely but after removing the whole alternator I found that the bolt has a slotted head that just fits into the "face". I put it back together and the alternator was working.

 

Attached a pic from yesterday. The three terminals are visible at the top but unfortunately I dont have one with the back of the plastic case - can take one tomorrow. Otherwise i think there are some pics earlier in this thread. I think i recall that the stud with the thin green/yellow wire was marked "W". The middle stud doesn't have anything attached to it.

 

As i say i tested it after this surgery and it was working. However im second guessing myself now and I'm wondering if, when testing, perhaps I was seeing voltage from my solar and the alternator hasn't been working since I got involved.

 

53 minutes ago, Dr Bob said:

Ivan, you didnt answer if it is a Beta 43.

If it is then seriously, look at the wiring loom connectors. I am not sure if the alternator field wire goes that way but when pootling along last year the rev counter stopped working and then when I moored up the engine wouldnt stop. It happens frequently on these engines. Pull the plug apart, clean the terminals and put back together tensioned with plastic tie wraps.

It's a Beta 38 but as I say, the wiring is a absolute mess. I tried to clean it a bit yesterday, the insulation tape was like tar. Awful. Fortunately white spirit dissolved it a bit.

 

I'm guessing by "wiring loom" you are referring to the white plastic terminal block - it has 11 connectors? I am not sure what most of them do but a goodly number arent connected to anything, or were connected to a black relay looking box that is completely rusted through and sitting on my workbench.

 

The alternator green/yellow wire avoids this block, disappears off down a conduit. I can try and trace where it goes tomorrow, or test that there is current. Any idea how I can test if this green/yellow wire is doing what it should?

 

56 minutes ago, nicknorman said:

The teeny green and yellow one is probably the initial excitation for the alternator, normally from the ignition switch via the warning light.

What is the "initial excitation"? Should I detect a current in this wire if the ignition is on?

 

57 minutes ago, nicknorman said:

Remind us, do you have just the one alternator and is there a working rev counter / tachometer?

There is a very small second alternator that I think was intended to feed the starter battery. I don't think it does anything, I fitted the VSR / voltage sensitive split charge relay when I bought the boat (which came without a domestic battery - so I stuck this 110Ah battery in with a VSR so I could at least use water pumps and a few LEDs, nearly two years later finally getting around to fixing it properly...)

 

59 minutes ago, nicknorman said:

Any markings on the case by the green/yellow wire terminal? Might be W or D+

Yes, I think in fact one terminal was W and the other was D+, will double check tomorrow - what do those letters refer to? There is even a small chance I mixed them up and put the green wire on the wrong one. Obviously I tried very hard to put it back together as I found it but also obviously something is wrong and - also obviously - I'm likely to be the problem!!

[MtB]

3 minutes ago, ivan&alice said:

No I don't have a rev counter

 

No rev counter ever installed? If no then paradoxically that helps. The little wire can only be the excitation lead.

 

Get yer digital multi meter out and turn the ignition ON but don't start the engine. Measure the voltage between the thin wire and the alternator frame/body. What is it? If 12.xV bung the clamp meter on and tell us the current.....

 

 

 

P.S. It's a racing certainty you were seeing the panel voltage earlier on....

 

 

[jetzi]

No rev counter on the boat. Not sure if there was once one, but as of now there is not one and there is no rev counter shaped hole anywhere.

 

Thanks Mike. I'll do these checks tomorrow. How does the excitation work - is there a current flowing to the alternator through that green/yellow wire when the ignition is on but engine not running?

[Alan de Enfield]

Something for the future :

 

Change out the 14v regulator (in the alternator) for a 14.4v or 14.6v, it'll help get your batteries better charged.

 

 

 

 

 

 

Edited April 13, 2020 by Alan de Enfield

[jetzi]

2 minutes ago, Alan de Enfield said:

Something for the future :

 

Change out the 14v regulator (in the alternator) for a 14.4v or 14.6v, it'll help get your batteries better charged.

 

 

 

Thanks Alan, in the not too distant future I'm going to need to do something to the regulator to ensure that it won't overcharge my lithiums. So I'll visit that soon.

[MtB]

2 minutes ago, ivan&alice said:

No rev counter on the boat. Not sure if there was once one, but as of now there is not one and there is no rev counter shaped hole anywhere.

 

Thanks Mike. I'll do these checks tomorrow. How does the excitation work - is there a current flowing to the alternator through that green/yellow wire when the ignition is on but engine not running?

 

Yep you've got it. You're looking for 2 or 3 Amps roughly, but the exact value is not critical, as long as there is a bit of current flowing.

 

If you get that, then start the engine and give it a good rev, then measure the voltage on the big fat wire terminal. Hopefully will be 14.4Vdc.

 

Mind the vee belt!

 

 

 

 

[Alan de Enfield]

Just now, Mike the Boilerman said:

Hopefully will be 14.4Vdc.

His regulator is only 14v

[MtB]

Just now, Alan de Enfield said:

His regulator is only 14v

 

14V is the same as 14.4V, when measured by an engineer.

 

 

Did you mean 14.0V..???! 

[Alan de Enfield]

Just now, Mike the Boilerman said:

 

14V is the same as 14.4V, when measured by an engineer.

 

 

 

One of these ?

 

 

 

[MtB]

Just now, Alan de Enfield said:

 

One of these ?

 

No that's an engine ear. 

 

Totally different, silly!!
 

[Alan de Enfield]

Just now, Mike the Boilerman said:

 

No that's an engine ear. 

 

Totally different, silly!!
 

Sorry, my eyes don't work so well so I was just going by the sound

[Tony Brooks]

9 hours ago, Mike the Boilerman said:

 

Yep you've got it. You're looking for 2 or 3 Amps roughly, but the exact value is not critical, as long as there is a bit of current flowing.

 

If you get that, then start the engine and give it a good rev, then measure the voltage on the big fat wire terminal. Hopefully will be 14.4Vdc.

 

Mind the vee belt!

Yep you've got it. You're looking for 2 or 3 Amps roughly, but the exact value is not critical, as long as there is a bit of current flowing.

 

 

 

 

 

 

Not sure that is correct. Yes the rotor will take 2 to 3 amps when running but that comes from the field diodes unless its a six diode machine. Ignition on and engine stationary the current will just be what has got past the warning lamp so at 2.2 watts that will b e about 0.2 amps and when the engine is running it shoudl be zero apart from on a six diode machine.

 

The Lucas test for the warning lamp circuit on 9 diode machines is to disconnect the D+ (warning lamp wire) from the alternator and check the voltage with the ignition on as Mike said several posts ago - expect 12V. If you leave the cable connected expect zero volts but its not a valid test. A quick and dirty test is to pull the D+ wire off the alternator and touch it to the alternator frame with the ignition on - expect the bulb to illuminate. If it does put the wire back on and it shoudl stay illuminated. If it does not then there is an alternator fault. Probably brushes or worn slip ring.

 

I do not immaculately recognise the alternator and I can't see a second diode heat sink plate so hopefully @Sir Nibble will pop along to clarify things.

[nicknorman]

10 hours ago, ivan&alice said:

What is the "initial excitation"? Should I detect a current in this wire if the ignition is on?

 

Yes, I think in fact one terminal was W and the other was D+, will double check tomorrow - what do those letters refer to? There is even a small chance I mixed them up and put the green wire on the wrong one. Obviously I tried very hard to put it back together as I found it but also obviously something is wrong and - also obviously - I'm likely to be the problem!!

 

Most alternators require “initial excitation”. This is some current sent through the rotor (field) to generate some magnetism, so that when the rotor rotates it generates some current in the stator (the bit that actually outputs the power). Once spinning,  current from the stator is fed into the rotor via the regulator and the initial excitation is no longer required - it has become self-sustaining.

 

The W terminal is the output from one winding of the stator. It is an ac voltage whose frequency is proportional to engine rpm and thus is used to operate a tachometer.

 

The D+ terminal is the output from the rectifier that is used to convert the ac from the stator, into D.C. to feed the rotor (via the regulator). This is where the “initial excitation” current is fed into, normally by means of a bulb fed from the ignition switch. If there is definitely no bulb, someone could have replaced it with a resistor.

 

If the wire that should have been on D+ is now on W, the alternator won’t work. I suggest disconnecting the green/yellow wire and measuring the voltage on it. I would expect to find zero volts with the ignition off and around 12volts with the ignition on. If so, this needs to be connected to D+. If not, we’ll need to think again.

 

Once it is connected to D+ one would expect some current to flow in it with ignition on but engine not running, but not a huge amount, maybe 1/2 amp or less.

 

Also worth mentioning that since you have 2 alternators, the normal means of switching the second (large) alternator is via a relay. So when you switch on the ignition, this powers the smaller alternator’s D+ terminal (usually via a bulb) from the engine battery, and also operates a relay that connects the larger alternator’s D+ to the domestic battery via another bulb (or resistor).

[MtB]

59 minutes ago, Tony Brooks said:

 

Not sure that is correct. Yes the rotor will take 2 to 3 amps when running but that comes from the field diodes unless its a six diode machine. Ignition on and engine stationary the current will just be what has got past the warning lamp so at 2.2 watts that will b e about 0.2 amps and when the engine is running it shoudl be zero apart from on a six diode machine.

 

The Lucas test for the warning lamp circuit on 9 diode machines is to disconnect the D+ (warning lamp wire) from the alternator and check the voltage with the ignition on as Mike said several posts ago - expect 12V. If you leave the cable connected expect zero volts but its not a valid test. A quick and dirty test is to pull the D+ wire off the alternator and touch it to the alternator frame with the ignition on - expect the bulb to illuminate. If it does put the wire back on and it shoudl stay illuminated. If it does not then there is an alternator fault. Probably brushes or worn slip ring.

 

I do not immaculately recognise the alternator and I can't see a second diode heat sink plate so hopefully @Sir Nibble will pop along to clarify things.

 

I suggested 2 to 3 amps because there is no warning lamp on this installation. On reflection though, I'm not sure why I think that is the current that would flow with the WL short circuited.

 

Another possibility is the alternator self-excites and the little green and yellow wire is for something else. 

 

 

[nicknorman]

25 minutes ago, Mike the Boilerman said:

 

I suggested 2 to 3 amps because there is no warning lamp on this installation. On reflection though, I'm not sure why I think that is the current that would flow with the WL short circuited.

 

Another possibility is the alternator self-excites and the little green and yellow wire is for something else. 

 

 

I think alternator rotors typically have a resistance of 3 or 4 ohms, so you are close. I would have said 3 to 4 amps. But we don’t know that the wire is connected directly to 12v, it might be through a resistor.

 

Connecting it to 12v isn’t a good idea, apart from the increased battery drain with the ignition on it means that the alternator starts to produce power (and thus drains mechanical power) from a very low rpm, ie below idle, making starting more difficult.

 

And, if there is a long delay between turning on the ignition and starting the engine, 36 to 48 watts is quite a bit of heat to dump into the interstices of an alternator that isn’t spinning.

Edited April 14, 2020 by nicknorman

[MtB]

7 minutes ago, nicknorman said:

I think alternator rotors typically have a resistance of 3 or 4 ohms, so you are close. I would have said 3 to 4 amps. But we don’t know that the wire is connected directly to 12v, it might be through a resistor.

 

Connecting it to 12v isn’t a good idea, apart from the increased battery drain with the ignition on it means that the alternator starts to produce power (and thus drains mechanical power) from a very low rpm, ie below idle, making starting more difficult.

 

And, if there is a long delay between turning on the ignition and starting the engine, 36 to 48 watts is quite a bit of heat to dump into the interstices of an alternator that isn’t spinning.

 

 

With no warning lamp, no tachometer and an unknown alternator, possibly self-exciting, this sounds like a DY bodge-up by the preceding owner, frankly.  I think first we need to investigate and pin down the function of this oddly-coloured thin wire. I would not expect an excitation connection to have green/yellow striped insulation.

 

My Leece Neville alternator happily self-excites, so they are out there in the real world, not just a theoretical possibility.

 

 

[Sir Nibble]

First, ignore everything you have been told so far. That's a six diode alternator and none of the above is applicable.

Not surprisingly I'm not at work. Let me have a browse through a parts list and see what I can find out.

[Tony Brooks]

3 minutes ago, Sir Nibble said:

First, ignore everything you have been told so far. That's a six diode alternator and none of the above is applicable.

Not surprisingly I'm not at work. Let me have a browse through a parts list and see what I can find out.

Thanks Sir N. I had a strong feeling it was a 6 diode machine, hence my qualification re 6 or 9 diodes.

[MtB]

34 minutes ago, Tony Brooks said:

Thanks Sir N. I had a strong feeling it was a 6 diode machine, hence my qualification re 6 or 9 diodes.

 

I've not really drawn any distinction between the two as a user, until now.

 

So from what Snibs says (i.e. ignore everything said so far in the thread), a six diode works in a completely different way? 

 

 

[Sir Nibble]

What does this mean?

"In doing so I managed to loosen the terminal that comes out of the alternator. I thought I'd broken it completely but after removing the whole alternator I found that the bolt has a slotted head that just fits into the "face". I put it back together and the alternator was working."

I see no slotted heads and don't know what you mean by the "face".

The alternator is a Lucas/Marelli machine and should self excite. The main +ve stud clamps a terminal from the regulator to the +ve heatsink and the regulator should energise the rotor from this terminal in response to detecting an AC pulse indicating the alternator is turning. So long as there is a good battery supply to that main terminal it should work. Usual fault is that the slip ring wears out and oil contamination accelerates that process but I don't see copper debris in the picture. If you can lay your hands on a small test lamp and connect it from +ve to D+ (the small terminal in the picture with the nut on) then let us know how it behaves.

[nicknorman]

Just now, Mike the Boilerman said:

 

I've not really drawn any distinction between the two as a user, until now.

 

So from what Snibs says (i.e. ignore everything said so far in the thread), a six diode works in a completely different way? 

 

6 diode machines don’t have a separate means of generating the field current (ie the 3 field diodes are not present). They may have a warning light but it isn’t part of the initial excitation. The field current effectively comes from the B+ terminal. There has to be a means of stopping the field current flowing when the alternator isn’t rotating. I’m not sure how this is done on a simple alternator, perhaps there is a switched power signal (from the ignition switch) to wake up the regulator, or maybe it just sits there looking for an output on one of the phases (when the alternator starts rotating). I think these are the type of alternator which can be prone to using more than their fair share of juice when everything is (should be) off.

 

The chip I’m using for my smart alternator regulator is designed to work with a 6 diode alternator, but it has a microprocessor inside, permanently connected to B+, that “sleeps” with zero field current (electronics consuming about 1/2 milliamp) until it is either “woken up” over the LIN interface (which would normally come from the vehicle ECU) or detects rotation by means of one of the phase outputs and some residual magnetism. It is physically simpler but relies on modern microelectronics to work.

[jetzi]

Results of the above investigation:

The green/yellow wire is connected to the W. There is nothing connected to the D+ terminal.

 

The green/yellow wire shows 12V (13.9V, since the solar charger is connected) between the green wire and the positive terminal of my battery (both starter and domestic). This is the case regardless of whether ignition is on, off or engine is running.

 

The green/yellow wire shows no current, regardless of whether the ignition is on, off or engine is running.

 

The fat red wire shows no current, regardless of whether the ignition is on or off. I'm seeing about 2A of current when the engine is running, I'm not sure if this is significant. Is there a chance my small battery is just fully charged and the alternator is "shut off" somehow? (It's a sunny day here in Hertfordshire and my MPPT is showing "Float".)

 

Since I have no tachyometer and it's very unlikely that my alternator is a fancy "self-exciting" type, I switched the wire to the D+ and tested current again, in ignition off, ignition on and engine running positions. Didn't seem to make a difference.

 

I can also provide figures from the BMV if that would help - please let me know what would be helpful?

 

Summary table:

 

Green wire:	Measurement	Ignition Off	Ignition On	Engine Running
Disconnected	Voltage: green wire and + starter battery	13.13V	13.07V	14.54V
	Voltage: green wire and + domestic battery	13.95V	13.95V	13.95V
	Current red wire	0.3A	0.3A	2.3A
Connected W	Voltage: green wire and + starter battery	13.18V	13.19V	14.03V
	Voltage: green wire and + domestic battery	14.00V	13.99V	13.99V
	Current green wire	0.04A	0.06A	0.04A
	Current red wire	0.04A	0.05A	2.2A
Connected D+	Voltage: green wire and + starter battery	13.26V	13.26V	13.58V
	Voltage: green wire and + domestic battery	13.97V	13.94V	12.93V
	Current green wire	0.04A	0.02A	0.01A
	Current red wire	0.04A	0.08A	2.1A

[MtB]

5 minutes ago, ivan&alice said:

Since I have no tachyometer and it's very unlikely that my alternator is a fancy "self-exciting" type

 

But Snibs has positively identified it as self exciting.

 

Have you tested the alternator in the dark? That 13.9v from your solar will be fooling your 14.0V regulator into turning the alternator OFF.