Put on your thinking caps

[Reculver Vicar]

HI All,
Maurice's health is improving;
I have replaced the clutch adjustment rod so I can now drive him.
I have removed the dynamo and put on a shiny new alternator.
He starts enthusiastically.
BUT
(Why oh why must there be buts??)
the little ammeter in the car shows that there is a discharge when the headlights are on, as one would expect,
but no obvious sign of input when lights are not on and engine running and revved.
The little red light comes on at ignition but then goes off as it should.
Somewhere something is not right.
What else could if possibly be?
I had wondered if it was the power lead coming from the indicator stalk which had been used to run a radio but I have clipped that off at the junction box so there's no worry there (is there?)
or is the heater blower wires...both of which are hanging free....but as it's not therefore connected in any way surely it's not them either (is it?).
AND
whilst your brains are being picked, to what do I connect those 2 heater blower wires so that I might get even a modicum of warmth inside the car.
Chicken John (STAR) sorted the red light problem before the dynamo was removed......and the fix lasted several days, during which time the ammeter needle went well into the charge side, but then the red light came back on for no apparent reason, and the needle went back to 12 o'clock or even 11 when the lights were used.
After Christmas will be my next chance to play....and I shall have engineer/army son to help....but YOUR advice would be most useful.
I do now have access to a BMC Workshop manual so things might become clearer!

Merry Christmas to you all and a Happy Healthy Peaceful and Prosperous New Year too
Ronald

[bmcecosse]

It's not clear what the problem is - with headlights ON and engine running - are you saying there is a DISCHARGE showing on the ammeter? Or is it just bang in the middle - which is fine........

[KeithGSY]

I suspect your alternator is feeding power directly to the battery and not through the ammeter. The meter is only showing current going to the cars systems. To put that another way, is the big wire from the alternator going directly to the battery (as it should)?
Ammeters are not good in alternator systems as they cause a voltage drop between battery and alternator which messes up the electronics in the alternator. Battery condition voltmeters are usually fitted instead on alternator cars. You need to trace where the (non original equipment) ammeter is connected into the circuit.

[MarkyB]

I think the battery is fully charged, and the alternator is having no problem supplying power for the lights.

[bmcecosse]

" Ammeters are not good in alternator systems as they cause a voltage drop between battery and alternator which messes up the electronics in the alternator. " Amazing - certainly a new one on me. I had better nip out and tell my alternator to look out! Strangely - it's been fine with my ammeter for the last 10 years or so.........

[kennatt]

mines been ok for the last 15 years If the ammeter is wired correctly ie heavy gauge wire(Same thickness as battery leads)from the alternator output to the ammeter and then to the positive side of the battery , in some case via the solenoid, then you should get a + reading when the engine is running with lights on,if it goes to negative it could be that the ameter is connected the wrong way round since they also show direction of the current as well as the charge rate ,swap the connection to it and see if it shows positive under load.

[IslipMinor]

Never heard that before and vehicle and other manufacturers have certainly been fitting ammeters with alternators for 40+ years, expecially commercial vehicles and marine applications. The one on our Minor has been fitted for 40+ years, with an alternator, and the only failure has been one front bearing ~10 years ago.

If you have a 'moving coil' ammeter, which is very sensitive, you can see the ammeter respond to the changing loads instantly, before returning to whatever charge it was making before the load was applied. Fully charged it will show '0', of course, and on idle it will depend on the applied load, the idle speed, alternator size, alternator pulley size etc.

Ronald,

How have you wired in the ammeter? It sounds as if it is not seeing everything properly.

[Reculver Vicar]

Right chaps, thanks for all that!
Headlights were good and bright yesterday when I tried them.
Little dial (is an ammeter then...who knows, I don't...but I think it is) stays in the middle or slightly to the discharge side.
When the problem was briefly fixed the needle did go right to the right hand side.
I have no idea who fitted the dial....it's just there, on the right hand side of the steering wheel fascia.
I'll have a poke about and see what i can find.
presumably if I remove it sensible there will be n o problems.
Then I can just drive around in a state of bliss until the battery dies!
Thanks all
best wishes
Ronald

[KeithGSY]

If you remove the ammeter remember it is intercepting the power feed to the car so the original connection has to be remade.

For you technical people out there, If you think back, ammeters diappeared when alternators came in in the late sixties. On commercial installations there is usually a voltage feedback to the control electronics but on simple alternators this is combined with the output wire. Fortunately most things survive abuse and few people outside the car manufacturers design departments would realise there was a change in battery life.

[bmcecosse]

Don't remove that ammeter! Just do this simple test for me - switch on the headlights - what does the meter show? Now start the engine and rev up - (lights still on) - what does it show now?

[IslipMinor]

Ronald,

If the 'little dial' is an ammeter, it will have a scale that has '0' in the middle and -xxA to the left and +xxA to the right, e.g -30A 0 +30A.

If you do decide to disconnect it, disconnect the battery first and remember that all the current, apart from the starter motor, can flow through the ammeter, so the new connections you make must be very good indeed - electrically and mechanically.

Other than showing apparently misleading readings, if that is all I would be inclined to leave it be, as without the right knowledge and tools, you could cause serious problems, or even a fire!

Anyone in the Herne Bay area could help out??

[rayofleamington]

Amazing - certainly a new one on me. I had better nip out and tell my alternator to look out!

Personally I think the idea of wiring the full electrical output through a single point on the dash is a bit risky ( it would never be done on modern cars ) and is just adding more possible failure modes rather than helping.
A voltmeter would tell you plenty and with less risk. With a suitable alternator you just need to know if it's working or not unless it's overcharging - all of which can be seen with a voltmeter.

[bmcecosse]

It can indeed - but these are Classic cars , and cars of that era had ammeters. It works well - tells me exactly what's going on. I have several 'battery condition' meters rattling around somewhere - I even have one attached to a cigar lighter plug - for plug-in diagnosis on other cars.

[mattyb]

I've got one of those "ciggy lighter battery condition indicators" that bmcecosse refers to ! was my late dads - used it on his Fiat 128.

Can you put a meter across the battery terminals and take three readings ? - first with engine off, 2nd with engine on, 3rd with engine and lights on ? - battery should still receive a positive charge on 2nd and 3rd greater than first reading ??

[Reculver Vicar]

Okay,
I have been for quite a drive round my churches this afternoon;
dared to put on the side lights too!
Even used the headlights when going into the garage.
When the lights go on the needle goes to the left - the discharge side; with side lights it goes half a notch, and with full beam it goes 2 whole notches;
if I rev the engine when the lights are on it makes no difference whatsoever to the behaviour of the needle.
I don't have the correct thingy to give you any readings!
(But I DO have ramps and axle stands for Christmas!! Yes!)

[Reculver Vicar]

THANKYOU for the two wiring diagrams.
I'll compare yours for the alternator with the one sent by Bull Motif.
and the other one actually tells me how to connect the heater; and presumably, as the wire is still attached at the valve, and the valve is opening and closing freely, yet there is no way of making that happen from the control inside the car....the wire must be disconnected at the control in the cab? Yes?
And is there a patent method for getting the little black nobble off the control lever so i can actually fully remove the whole of the front plate?
Thanks in advance for your help.
Ronald

[kennatt]

you talk about a problem RED LIGHT in original posting and that the problem was solved BUt that was with a dynamo,I suspect you are talking about the control box.You do not now need this box since you have fitted an alternator,the controls are inside the alternator, Did you fit the alternator yourself,are you sure you have wired it up correctly,if you have run it through the control box,Somehow??,you will get all sorts of funny problems.One good old test is to go out,Now if you can whilst dark,switch the lights on then start the engine,a good battery fully charged will start it,and with the lights pointing at the garage wall rev it up,the red light should go out if not allready so,and if the alternator is charging you should see a marked brightening of the lights.If the lights do not brighten then the alternator is not charging for whatever reason,Before you go any further do this and report back

[Reculver Vicar]

Hi,
Thanks for that.
Right......
headlights on....quite bright.
Engine started easily.
Revved the engine and red light went out
headlights did get brighter as I revved - quite discernibly,
and when I lifted my foot and the engine returned to idle the lights got markedly dimmer again.
the needle on the little ammeter pointed to one notch on the discharge side.

Yes I fitted the alternator myself carefully following the Bull Motif instructions.....which were actually very clear and accurate as far as I could tell.

The little black box....the regulator...with the connections labelled A B C D etc underneath is where all the wires go.
I have connected it exactly as I was instructed....three of the original wires from the right hand side of the box are not now used...so they are disconnected and sealed off with tape.

Maybe the ammeter is lying; perhaps all is well and simply because the alternator is there the ammeter is having a crisis!??

Best wishes
Ronald

[Reculver Vicar]

I suspect your alternator is feeding power directly to the battery and not through the ammeter. The meter is only showing current going to the cars systems. To put that another way, is the big wire from the alternator going directly to the battery (as it should)?
Ammeters are not good in alternator systems as they cause a voltage drop between battery and alternator which messes up the electronics in the alternator. Battery condition voltmeters are usually fitted instead on alternator cars. You need to trace where the (non original equipment) ammeter is connected into the circuit.

The big wire goes from the alternator to the solenoid and then straight to the battery....that's what Bull Motif suggested.....

[bmcecosse]

Can only assume when you wired in the alternator - you have bypassed the ammeter. So it shows only discharge from the battery - the charge from the alternator going directly yo the battery. And yes - it IS charging , just not showing up on the ammeter. The BM wiring wouldn't take an ammeter into account...........unfortunately.