The Fordson Tractor Pages Forum

I have changed from a dynamo to an alternator on my Super Major 1963
i understand i need to swap the wires over on the alternator but what wires go back to the battery

thanks jim

Hi Jim,
Have you switched the tractor to negative earth?

not as far as i know
battery terminals are Pos to solidiod and neg to chassis

Ok, Neg to chassis is already negative earth.
Not knowing what alternator you have, there is generally one large connector and one or two smaller terminals. The large terminal would go to the battery positive. the smaller terminal should go to the key live, but it must go via a bulb (the bulb/holder must be insulated from any metal to metal contact with the chassis). This is known as the exciter wire. With the engine stopped and key off, the bulb will be off. When you turn the key on, +ve from the key will light the bulb, as the small alternator terminal will be -ve and earth through the alternator. When you start the engine, and the alternator starts to charge, the small -ve terminal becomes +ve and extinguishes the bulb. This your charge fail warning light. Once running, a test meter across the battery should hopefully show 13 - 14V.

Depending on the alternator and pulley size, you may need to rev the engine (when it's warmed up) to get the light to go out and the alternator to start charging. I only say this as a friend has one with an alternator conversion and the light won't go out unless you rev the engine above half throttle, then it goes out and stays out even at tickover

Thanks Guys for the info, I will give it a try this weekend
Cheers Jim

Thanks John, well remembered. Most '000 and 600 series had to be revved a bit to get the light out.
I'm hoping someone will be along shortly to either confirm or correct my wiring description.

Looks good to me, think you just about covered it. Hope the hydraulics are still going strong on your major!

Hi John, sorry, penny's just dropped! Nice to hear from you. Yes she's doing well, lifted everything I've asked of her without question and currently running a Palax firewood processor. Unfortunately a medical issue has put a stop to me doing any tractoring at the moment - and in ploughing match season as well still, never mind, lets someone else win something for once, and probably stopped me from making a fool of myself.
Apologies Jim, gone a bit off topic.

Hi John
Just checked my wires on the alternator and I’ve found the small wire going up to the bulb
But on the other terminal I’ve got 2 wires one very thick (bit like me) and one very thin both yellow/white and at the moment both taped off
I’m going to put both of these direct to pos on the battery and see if it’s charging and the gen light goes out
I’ll let you know

Thanks
Jim

Hi Jim, just make sure that your tractor has been changed to negative earth
John

Hi
I have connected the wires as suggested but have no charging
I took the wires off the alternator and put a meter across the terminals and got nothing coming out of the alternator
I have three spade terminals on my alternator 2 large spade and one smaller
Showing nothing at any terminal I have swopped the wires around these terminals and still nothing
Power is flowing to the alternator from the battery
Is there any simple test I can do to check if alternator is working
It looks very old and worn
I’m determined to get this charging even if I go back to a Dynamo and control box

Thanks
Jim

It looks like your alternator is needing attention.
Sandy

Sounds like the alternator may be defunct.
If you have 2 serviceable batteries, place battery 1 on the tractor and connect in the normal way. Remove all wires from the alternator and tape them up. Place battery 2 on the floor near lhf wheel.
Using a jump lead, connect the -ve terminal of batt 2 to the tractor near the alternator.
Connect one of the large alternator terminals to the +ve post on batt 2.
Connect the small alternator terminal to a bulb, then on to +ve post on batt 2. The bulb should light.
Connect a voltmeter across the +ve and -ve terminals of batt 2.

Before going any further, what you should now have is effectively an electrical system to start the engine, and a totally separate system connected to the alternator. The bulb should be on, and the meter should read 12 to 12.5 volts.

Start the engine.
The bulb may go out and the volts start to rise to 13 or 14 volts. Alternator is good.
If the bulb stays on (not unusual), run the engine speed up to around 2/3 of max revs. If the bulb goes out and the volts come up, alternator is good, but could do with a smaller pulley.
Bulb stays on and volts don't change, alternator is suspect and is likely bin fodder.

As I thought Alternator is US
It has no markings on it
Anybody have any suggestions as to what Alternator I need to install in order to get the mountings right

Thanks
Jim

I recommend using the original dynamo and regulator.
Sandy

Thanks
Think I will but unsure which regulator to go for as Agriline list 4 different types for the super Major
Any thoughts on which one to go for

Thanks for your advice
Cheers Jim

For a Super Major you want a Lucas sealed regulator with the same terminals as your wiring has and mounting brackets to fit the air filter mountings. There are several dynamos too, up to 1962 a Lucas C39 variant was used, after that it was a C40 variant.
Sandy

Thanks for the info Sandy
I’ve sourced a Dynamo and Regulator from Agriline
And will attempt fitting on Saturday
Understand I’ll need to convert back to Positive Earth and about polarising the Dynamo

Once again thanks for all your help and advice on this matter

Regards
Jim

You will want to return to positive earth. Polarise the dynamo just to be sure it works properly (I would imagine it would be sold polarised, but it might not be).
Sandy

Hi Guys

Just to give you the latest and ask for more advice

Fitted a new Lucas Dynamo and a new regulator wired them all in
Swapped over to positive Earth
Polarised the Dynamo
Started her up
Gen light light on dash even with 3/4 throttle it stays on

I’ve put a meter across the battery and it’s still showing 12.8 not 13 or 14 I was expecting
Wired it all up as per Fordson wiring diagram

I had 3 wires at my Dynamo but only got 2 terminals one large Yellow/White and 2 thinner wires yellow white and red white I’ve joined these 2 together


Any thing else I’m missing or can check
Help would be appreciated

Jim

The red-white wire goes from the small dynamo terminal to terminal F, the thick yellow-white wire goes from the large dynamo terminal to terminal D, and the thin yellow-white wire goes from the large dynamo terminal to the red light on the dash. The two yellow-white wires are connected together at the dynamo end.
Sandy

Hi Sandy
Have swopped the wires like you said
Battery now charging all be it slowly maybe I was expecting it to show 13 or 14 ,volts immediately

However the gen light on the dash is still on despite having high revs

Try polarising the dynamo again, you might want to test the regulator too.
At 1000 rpm the dynamo should be comfortably over 24V (to do this disconnect terminals D and F at the regulator, connect them both to the negative lead of a voltmeter and connect the positive lead of the voltmeter to the earth lead on the battery, ensuring your voltmeter can read at least 30V).
The regulator should regulate at 15-16V (at full revs) depending on the temperature (the colder it is the higher the voltage needs to be), and should cut-in at 12.7V- 13.3V. I would recommend you fit a two way -30A to 30A ammeter between the wire and terminal A for all this (like the earlier Major ammeter) so you can see what the charging current is doing, it will show you the cut-out more accurately and give you a better idea of how it's working, Billy goes between 10 and 20 charging amps depending on the status of the battery.
Sandy