Jump to content

A127 alternator - intermittent fault


MtB

Featured Posts

I have a Lucas A127 cheap clone alternator on REGINALD, which has never charged a really flat battery at more than about 15 amps (according to the 30 year old ammeter fitted). Until NOW that is!

 

Now, after starting the engine, the ammeter swings up to almost full scale deflection, reading about 55 to 60 Amps. I think this is a true reading because the vee belt complains horribly by squeaking and squealing no matter how much I tension it. After a few minutes the charge rate drops to about 30 Amps and now the trouble starts. The ammeter reading randomly jumps up and down every few secondsbetween readings of approx 30 amps then falling to about 5 amps. The vee belt squeaking occurs during the 30 amp periods.

 

It continues to do this indefinitely, randomly switching the charge current up and down. During the low current reading the alternator output voltage reads about 13.4v using a digital voltmeter. During the 30 amp periods the voltage is 15.5v. Surprisingly high I thought. These values are from memory when I was fault tracing it yestarday so may not be bang on.

 

I infer from this the fault lies within the alternator. Does the board agree? Do I need a whole new alternator or is this likely to be a failing regulator module?

 

The alternator has only done a few hundred hours since new and it has never seemed to really charge the batteries fully. I initially put this down to the crappy wiring but now I'm wondering if the 60 amp charging I'm seeing intermittently is how it ought to work all the time.

 

All advice much appreciated. Thanks.

 

MtB

Link to comment
Share on other sites

First thing to check is that the earth connection is OK. Assuming the it's not an isolated-earth marine model, that means the engine to alternator mounting bolts, and the engine earth strap.

 

MP.

 

Thanks for your answer MP.

 

I checked this this yesterday and there seems to be a well-connected lead from the negative busbar back to the alternator chassis, connected via a mounting bolt. I'll examine and test it again though.

 

Maybe replace it as it is a bit thin but I doubt it being undersized would cause this. It does seem like a loose connection but if so, why would the alternator voltage be stable in each of the two 'flip-flop' conditions? Loose connections generally result in randomly flutting voltages IME.

 

MtB

P.S.no engine earth strap as the old vintage engine is bolted directly to the engine bearers.

Link to comment
Share on other sites

The forces on the alternator mountings depends on the output power of the alternator, so you could have a situation where the alternator is not producing much power and there's no much force making a connection and another stable state where the power and force increases, increases the contact pressure and reduces the voltage drop. It's a theory, anyway.

 

Best thing to test it is to put a multimeter on volts scale between the alternator case and a negative battery post - you should be able to see any volt-drop.

 

If that's not the problem, A127 regulators are both cheap and easy to replace.

 

MP.

Link to comment
Share on other sites

55-60 Amps is how it should work when the battery is well discharged so what you have now is better than what you had!

 

MP has covered all the connection bases- also worth looking at the voltage drop between the alternator + terminal and the battery + terminal. If this is high look at the voltage drop across such things as master switches, blocking diodes, relays et al. The other thing to look at is the ammeter. I guess that it's one of the type where the alternator cable runs to the meter and then to the battery. These are low-quality, low accuracy devices ( mostly made by the Prince of Darkness, Joe Lucas himself) so it would be worth trying a cable direct from the alternator to the battery. If the belt then squeals consistently it's the ammeter. Either do without, or buy one that has a shunt and re-wire the alternator to battery connection as short as possible. Should you have or be able to borrow a clamp-on DC ammeter then you might also use that to see what the current is doing.

 

I assume the alternator has not been modified for a battery management thing (Adverc or whatever?). If it has you can apply 12v to the flying lead from the regulator and it should go to full output. If it doesn't the alternator is banjaxed.

 

If it is the alternator probably either the regulator, or the slip-rings on the rotor and brushes on the regulator. It's cheap enough to replace the regulator for diagnostic purposes.

 

Take the regulator off the back (3 screws and one wire) and check that the copper slip rings the brushes run on are clean and in good nick. If not it's a specialists job.

 

If the regulator doesn't fix it and the cabling is OK then it's a service replacement job.

 

Tightening the belt should cure the noise, but you might need a new belt if it's been doing it a lot.

 

N

 

ETA the bit about the ammeter.

Edited by BEngo
Link to comment
Share on other sites

  • 2 weeks later...

Ok, thanks for the replies everyone. Here's an update.

 

I bought a clamp meter and the Lucas ammeter is returning roughly accurate results. The charging current definitely does leap up and down as indicated.

 

I've done a lot of testing of the cabling with a voltmeter and it is not in great condition and I find poor connections causing 0.1v and 0.2v differences all over the place but no one large/bad poor connection. However, I think I've discovered the cause of this massive 60amp charge rate - starter battery has a badly sulphated cell and while turning over the engine the terminal voltage was falling to 2.1v!

 

I suspected the cell was intermittently shorting so I fitted a new battery, and the 60A charge rate vanished and max charge rate from the alternator has now reverted to about 24amps, about what I'd expect.

 

However the high/low switching charge rate is still present, and the bad battery was just attracting my attention to the fault. The charge rate now randomly steps up and down between about 24amps and 8 amps.

 

Further testing with the voltmeter shows the alternator output is flip-flopping randomly between 14.1v and 15.8v. This suggests to me I need another new alternator. (This one is only two years old.) Does this seem a good diagnosis?

 

Is this alternator possibly repairable, with a new regulator module perhaps, or am I better off to just buy a whole new alternator?

 

Many thanks,

 

MtB

Link to comment
Share on other sites

Almost certainly just a regulator.

By the way, there is a 14.8V version available, may be worth fitting that or take the opportunity to slot a diode in the yellow lead whilst the reg is off to lift the charge a little.

 

Ok, thanks for your reply!

 

Any idea where I can get a 14.8v regulator from please? None listed on ebay and even googling returns nothing meaningful for me....

 

Or does your 'slot a diode in' suggestion do the same thing?

 

I'll do some more googling to see if I can understand more about how alternators work.

 

 

MtB

P.S. Any old diode, or something specific?

P.P.S. And which way around?!

Link to comment
Share on other sites

According to Charles Sterling, the ammeter needle bouncing is a rare, but known, problem with the A127 alternater, apparently it is called pulsing. I am assured that it does not mean the charge is pulsing merely the signal to the ammeter, but it is very annoying. Do you have an early Alternator Controller fitted, the later Digital ones correct this problem.


 

Ok, thanks for your reply!

 

Any idea where I can get a 14.8v regulator from please? None listed on ebay and even googling returns nothing meaningful for me....

 

Or does your 'slot a diode in' suggestion do the same thing?

 

I'll do some more googling to see if I can understand more about how alternators work.

 

 

MtB


P.S. Any old diode, or something specific?


P.P.S. And which way around?!

 

Give these people a ring, they will even supply the regulator with sensing wire( for Alternator Controller connection) soldered on. they also supply re-built Alternators :- http://www.vehicleelectricsshop.co.uk/

Edited by David Schweizer
Link to comment
Share on other sites

Thanks David. I don't think it can be 'needle bounce'. The high charge rate and low charge rate remain steadily indicated on the ammeter for a few seconds to 30 minutes long each, and are confirmed as accurate by my clamp ammeter around the charge wire.

 

Is the regulator with the extra wire the same thing as a 14.8v regulator then?

 

 

MtB

Link to comment
Share on other sites

No. The extra wire is there for a 'battery management system'. It allows the battery boiler to override the alternator's own regulator.

 

Almost any new A127 regulator will be set at 14.8 V, but I'm sure that Snibble will be along with a Cargo part number soon.

 

Failing that there's always the tractor regulator thread: www.canalworld.net/forums/index.php?s=9bb21675d733e5a55d5c8808ad9f2077&showtopic=25083 Wood Auto sell these quite inexpensively.

 

N

Link to comment
Share on other sites

Thanks David. I don't think it can be 'needle bounce'. The high charge rate and low charge rate remain steadily indicated on the ammeter for a few seconds to 30 minutes long each, and are confirmed as accurate by my clamp ammeter around the charge wire.

 

Is the regulator with the extra wire the same thing as a 14.8v regulator then?

 

 

MtB

 

The regulators do not come with an extra wire, you only need one added if you have an alternator controller, (or battery management system) .

 

I would certainly try changing the regulator, but don't throw the old one away until you have established that it is actually causing the problem. I did that once when a new reguator appeaerwed to fix an intermittent fault. When the fault returned later, I discovered that there was a dry joint inside the field wiring and the regulator (now in the bin!! ) was fine.

 

edited:- to clarify purpose of extra wire.

Edited by David Schweizer
Link to comment
Share on other sites

No. The extra wire is there for a 'battery management system'. It allows the battery boiler to override the alternator's own regulator.

 

Almost any new A127 regulator will be set at 14.8 V, but I'm sure that Snibble will be along with a Cargo part number soon.

 

Failing that there's always the tractor regulator thread: www.canalworld.net/forums/index.php?s=9bb21675d733e5a55d5c8808ad9f2077&showtopic=25083 Wood Auto sell these quite inexpensively.

 

N

 

Interesting that you use the derogatory term "battery boiler". I have heard others use it and can only assume that some people have had problems with them. I have had my Sterling Advanced Alternator Controller fitted for over eleven years and have never had any problem with batteries boiling or even overheating. Perhaps it is because some people only have cheap leisure batteies, I have a pair of heavy duty extra deep cycle US batteries (designed to operate golf carts and fork lift trucks) which are eight years old and still maintain a full charge, not cheap but better value in the long term,

Link to comment
Share on other sites

Give these people a ring, they will even supply the regulator with sensing wire( for Alternator Controller connection) soldered on. they also supply re-built Alternators :- http://www.vehicleelectricsshop.co.uk/

 

Ok, I've just ordered a new regulator from the link you gave. I called them to see what voltage theirs were set to, and they said 14.5v, and that there was no such thing as a 14.8v regulator for an A127. so I ordered their 14.5v version!

 

There is a very old (25 years I'd guess) 'battery boiler' installed but it can't be doing anything as there is no sense wire on the old alternator regulator. OR can it??? could it still be interfering and causing the charge voltage to intermittently jump up to 15.8v?

 

MtB

P.S. I'll be taking the old battery boiler out anyway soon. I find it hard understand what it is for and I don't like things I don't understand! In additon, there is no manual for it and google searches for it reveal nothing on the net.

Link to comment
Share on other sites

 

Ok, I've just ordered a new regulator from the link you gave. I called them to see what voltage theirs were set to, and they said 14.5v, and that there was no such thing as a 14.8v regulator for an A127. so I ordered their 14.5v version!

 

There is a very old (25 years I'd guess) 'battery boiler' installed but it can't be doing anything as there is no sense wire on the old alternator regulator. OR can it??? could it still be interfering and causing the charge voltage to intermittently jump up to 15.8v?

 

MtB

P.S. I'll be taking the old battery boiler out anyway soon. I find it hard understand what it is for and I don't like things I don't understand! In additon, there is no manual for it and google searches for it reveal nothing on the net.

 

If there is an Alternator Controller installed, I must have been connected at some time, but all the models that I know of use a field wire from the alternator. If your new alternator which was recently installed does not have a sensing wire, maybe the controller was disconnected when it was fitted. However, as precaution, I would check whether any other wires from the Controller are still in place, They probably won't interfere with charging, but It is worth checking .

 

As a matter of interest do you know what make the controller is, one of the earliest ones on the market was the Kestrel made by Acorn Engineering, that really was a battery boiler. A picture can be found here ( sorry can't get the picture alone to post):- http://www.ebay.co.uk/itm/marine-alternator-controller-Kestrel-/261235444318?nma=true&si=S5lncp%252FXA2SEwobmBSOv3epVaxM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

 

They no longer make it, but the full instructiions can be found here:- http://www.acornengineer.co.uk/kestrel_alt_controller.php

 

edited :- to correct the name of the wire coming from the alternator

Edited by David Schweizer
Link to comment
Share on other sites

It's NOT a sensing wire. The sensing wire should go to the battery positive. The wire stuck out of a modified regulator simply allows the charge controller to override the normal alternator regulator.

 

Also someone said if you connected it to 12V pos it would force the alternator to full output. I think that may well be incorrect in some cases because the charge controllers often connect the rotor brush to negative. It probably depends if the alternator's regulator is in the positive or negative side of the rotor.

Link to comment
Share on other sites

As a matter of interest do you know what make the controller is, one of the earliest ones on the market was the Kestrel made by Acorn Engineering, that really was a battery boiler. A picture can be found here ( sorry can't get the picture alone to post):- http://www.ebay.co.uk/itm/marine-alternator-controller-Kestrel-/261235444318?nma=true&si=S5lncp%252FXA2SEwobmBSOv3epVaxM%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

 

They no longer make it, but the full instructiions can be found here:- http://www.acornengineer.co.uk/kestrel_alt_controller.php

 

Yes spot on, it IS a Kestrel by Acorn engineering, and yes it is still connected except for the white wire. Looking at the wiring, I can't see any way it could be causing the intermittent 15.8v charging voltage, but I'll disconnect it anyway.

 

MtB

Link to comment
Share on other sites

It's NOT a sensing wire. The sensing wire should go to the battery positive. The wire stuck out of a modified regulator simply allows the charge controller to override the normal alternator regulator.

 

Also someone said if you connected it to 12V pos it would force the alternator to full output. I think that may well be incorrect in some cases because the charge controllers often connect the rotor brush to negative. It probably depends if the alternator's regulator is in the positive or negative side of the rotor.

 

Yes, sorry about that mistake. I have just checked the Sterling instructions and the correct name is a Field Wire

Link to comment
Share on other sites

  • 6 years later...

Hi did you get this sorted in the end. I have the same problem. If the battery is fully charged the. There's no problem. As soon as I start the engine with a low battery the lucas A127 starts to get hot and belt starts smoking. The rev counter stops working. 

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.