Charging light stays on

[pig]

When I start the engine, the oil pressure warning light and the charging light normally go out. Yesterday the charging light dimmed, but stayed on, and glowed more brightly as engine revs increased.

I have a Smartgauge and the starter and leisure batteries seem to be charging ok.

i checked the wiring as best I could, and then measured some voltages- one side of the charging bulb is at 12v from the +supply, the other side of the bulb is fed from one terminal on the alternator, presumably as the alternator turns, the voltage rises and the lamp goes out. This terminal also supplies the split charge Albright relay- this works as normal. However the voltage at this side of the bulb raises to 18v as the revs increase, thus the bulb glows.

is my alternator (a Lucas A127) knackered?

thanks for any help

Neil

[Tony Brooks]

Sounds like the voltage regulator has failed if that 18V is correct. These are easily replaceable and come with new brushes BUT the slip rings may be worn. Don't just drag the regulator straight off the back of the alternator or else you will snap at least one brush. You need to sort of twist it upwards so the brushes lift and clear the case, then pull/lift it out.

As its seems you are getting 18V from the warning lamp (D+) connection the field diodes are OK. If it were 18V on the main output terminal and less on the D+ then the high voltage could be caused by blown field diodes but unlikely in this case.

As normal check a ll terminal and connections, including battery posts for cleanliness and security.

[pete.i]

Not the easiest job in the world but not that difficult. I have done a couple of these and I buy my bits from Ebay. The complete alternator is reasonably cheap if you do not fancy doing the job. Complete refurb kits that include bearings etc are also available on Ebay.

https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2380057.m570.l1313.TR2.TRC0.A0.H0.TRS0&_nkw=Lucas+A127&_sacat=0

[pig]

Thanks for the replies. I'm in Stratford on Avon now, and heading back to Foxton. What will happen if I can't get a repair done? I'm not too concerned if I need a new alternator, but I don't want to bugger up the battery bank!

[Tony Brooks]

The fact that you have a contactor implies its a single alternator boat so if you have 18 volts at the D+ alternator terminal you will also have 18 volts ish at the batteries. Not  good, will cause excess gassing, and plate erosion. You must be at least a week or more from Foxton so  I would not leave Stratford until you have it sorted.

I have just googled "alternators stratford upon avon" and a specialist in Bidford came up. I also suspect any motor factors will supply you on an exchange basis. There has to eb a local supplier, repairer who will test it before doing any work on it. Spend soem time on Google/Online BT Phone Directory

[Tony Brooks]

Further thought.

If you have an accurate voltmeter that you can see from the helm you just MIGHT be able to limit the charging voltage by keeping the engine revs low but its a long way at tickover or just above, even if it works. If you have wet open cell batteries try to keep the voltage below 15 volts and check the batteries for needing topping up every day. If they are sealed do not even try it unless you can keep the voltage around 14.2 to 14.4 or less.

A long shot at best.

[pig]

Thanks again Tony,

I am able to measure the voltages at the leisure bank and starter battery via the Smartgauge. With the engine running, the voltages are pretty much the same, about 13.6v.

This makes me think the alternator output is down, normally I'd see about 14.4v or slightly above.

I am thinking that if I don't get a repair done, the batteries are not in danger of overcharging, so I will rely on my solar setup to keep the leisure batteries charged, and hope the starter battery gets sufficient charge from the compromised alternator.

Nevertheless I will have a mooch round S on A and see if there's a supplier.

thanks

Neil

[Tony Brooks]

In that case the 13.6V at B+  suggests the previous 18V is suspect UNLESS you have some form of battery sensing (not standard on an A127) and there is a problem on the main charging leads (+ & -), the battery leads (+ & -), or the sense lead. However the warning l;amp did glow so that tends to support the 18V measurement.

If there is no battery sensing via the likes of an alternator controller or an unusual A127 then we need to start again.

With engine running at about 1500 rpm measure:-

1. Battery voltage (bat + to bat - posts) on BOTH banks. (2 results needed).

2. Voltage at the main alternator output terminal (B+ to bat - post)

3. Voltage at warning lamp terminal on  alternator (D+) (D+ to battery - posts)

4. Voltage with meter connected between B+ and D+

5. Voltage on meter when connected between B+ and battery + post (it shoudl notbe much).

6. Ditto between Alternator negative terminal (B-) or case and battery - post.

Please make sure you tell us about all the charging equipment you have. We know you have the Albright, presumably as a split charge relay and the A127 but is there anything else?

 

[Tony Brooks]

Just realised. That 13.6 volts could well be because the batteries are well discharged and the alternator is operating at maximum output. In this state the design of the alternator automatically reduces the voltage to keep the output Watts at their design limit.

I thin it is likely to creep up and up as the batteries charge and the output reduces.

[pig]

OK Tony, here are the voltages as requested, but first let me describe my setup; it's a simple single alternator feeding a single starter battery and 4 leisure batteries. The Albright contractor joins the two banks together when the engine runs, and drops out when it stops. There is no voltage sensing gubbins apart from built in to the alternator, no Adverc, nothing. 

I have a 500w solar setup (2x250w) feeding the leisure batteries via a 40A Tracer MPPT controller.

The voltages are:

1 13.8v at starter battery, 13.3v at leisure bank. (These agree with the Smartguage readings)

2 13.9v at B+

3 18.1v at D+

4 4v between B+ and D+

5 0.06v between B+ and batt +ve 

6 0.05v between alt - and batt -

These were read soon after starting the engine, now it's been going for about 25 mins, the battery voltages have gone up to 13.9 and 13.6 (starter/leisure), and the smartgauge has gone from 64% to 67% charged. The lack of sunshine makes me believe it's the alternator doing the charging!

Thanks again

Neil

[Tony Brooks]

That 4V between B+ and D+ is a strong indication you have a diode failure.

I do not like the 0.6V of voltdrop between the alternator output and the domestic bank but for now that can wait, lets not complicate things. However I have doubts about that reading because the voltdrop on the that lg of the circuit you measured at less than 0.1 volt. In fact its only 0.11V on both neg and pos legs together.

Reading 2 & 3  confirm reading 4.

I suspect a main negative diode or a bad solder joint (Snibs may well take a different view). 13.9 volts will eventually recharge the battery given long enough so I thunk that you could move towards home as long as you ensure that you do not get more than about 14.5 volts on either battery bank. Trouble is its a single alternator boat and we know there is every chance the alternator is faulty so if it fails totally on say the Watford summit getting help might not be so easy.

[WotEver]

8 minutes ago, Tony Brooks said:

I do not like the 0.6V of voltdrop between the alternator output and the domestic bank...

You misread it Tony, it's 0.06V. 

[Tony Brooks]

No, that's the actual voltdrop as measured in parallel on the cable. Look at reading 1 & 2 - 13.9 at B+ and 13.3 at the domestic battery positives - that's 13.9 - 13.3 = O.6v voltdrop.

I suspect reading 5 is between B+ and the engine battery positive with the main charging lead running to the engine bank. If so I suspect the contactor contacts are dirty or not making firm contact. We know he has a Smartguage and an Albright contactor so I suspect he may have a  Smartbank and I do not know hoe Gibbo recommends wiring the charging circuit, but I would definitely have the main charge going to the domestic bank for the reasons we have discussed so many times before. Its even possible the link cables for the contactor are undersized.

Its all remote diagnosis so its open to error but the difference between calculated voltdrop and measured voltdrop stood out for me.

 

PS - Pig, ignore this bit of the discussion, lets get the main problem sorted.

Edited September 10, 2017 by Tony Brooks

[WotEver]

18 minutes ago, Tony Brooks said:

No, that's the actual voltdrop as measured in parallel on the cable. Look at reading 1 & 2 - 13.9 at B+ and 13.3 at the domestic battery positives - that's 13.9 - 13.3 = O.6v voltdrop.

Oh yes, you're quite right, that's the Albright circuit - must be weedy interconnects. 

Although I guess it could be pitted contacts. As you suggest, one problem at a time then let's get the alt feed swapped over. 

Edited September 10, 2017 by WotEver

[pig]

Ok I hear what you're saying about the connection between the alternator and the batteries- it would be better to connect it to the leisure bank, rather than the starter battery, yes? If so that's an easy swap.

But the alternator problem- the blown diode/unsoldered joint, is that in the (relatively easy to replace) regulator, or in the bowels of the alternator?

[WotEver]

3 minutes ago, pig said:

Ok I hear what you're saying about the connection between the alternator and the batteries- it would be better to connect it to the leisure bank, rather than the starter battery, yes? If so that's an easy swap.

But the alternator problem- the blown diode/unsoldered joint, is that in the (relatively easy to replace) regulator, or in the bowels of the alternator?

Yes, in due course swap the feed over. 

The alternator problem means replacement or repair. It will probably be cheaper to replace than to repair, Plus a replacement will have new bearings etc and a 12 month warranty. 

[Tony Brooks]

21 minutes ago, pig said:

Ok I hear what you're saying about the connection between the alternator and the batteries- it would be better to connect it to the leisure bank, rather than the starter battery, yes? If so that's an easy swap.

But the alternator problem- the blown diode/unsoldered joint, is that in the (relatively easy to replace) regulator, or in the bowels of the alternator?

If i am right in my diagnosis the problem is deep inside the alternator. I'm with the other Tony, replace it, it will be far easier but make sure you keep the pulley you have now unless the new alternator comes with the same sized pulley but that's doubtful.

Rather than just swapping the main feed from engine battery to domestics I would try to find the voltdrop, solve that, then do the swap. Just swapping would move sub-optimal charging from the domestic bank to engine bank although I doubt it would have a significant effect because the charging current will generally be far lower through the Albright.

Edited September 10, 2017 by Tony Brooks

[pig]

What voltages should I expect at the B+ and D+ terminals on a replacement alternator?

[Tony Brooks]

only a few mV, less than 1V.

[Sir Nibble]

16 hours ago, pig said:

What voltages should I expect at the B+ and D+ terminals on a replacement alternator?

The same give or take quarter of a volt at about 14 1/2V. Clearly lost a main diode but also the regulator! Most likely the diode failed right after the reg. New alternator.

[pig]

Thanks everyone.

New alternator ordered. Being delivered to a friend who can get it to me in case it fails completely on the way back.

[Tony Brooks]

Just watch those charging volts as the hours go by each day.

[pig]

Update:

above mentioned friend came out with new alternator. Supposed to be straight swap but terminations different; needed to get busy with my crimping tool!

Fitted and working. No more red light when running, voltages back to normal level.

Thinking about it I think the alternator succumbed after a brief engine overheat (low coolant level, ahem).

I also swapped over the feed to the leisure bank as suggested. Thanks for the advice.