Alternator help

[Newlands]

I’ve managed to find a wiring diagram for the alternator version of this tractor, so tomorrow I’ll start by checking the wires between the IND terminal and the lamp, and then between the lamp and the starter. The loom is actually very difficult to get to as it disappears under the hydraulic tank and battery box, so if any of them need replacing I’ll have to re-route them.

 

[Stueeee]

Could be that your replacement regulator is a 'self exciting' type. These sense the the change in induced current in the windings as the alty rotates. At a pre-determined rotation speed derived from the frequency, they provide the seed voltage from the 'B' terminal. Google 'one wire alternators' for chapter and verse on these.

 

[m_c]

If the warning lamp comes on when you ground the warning lamp wire at the alternator, then there is nothing wrong with the wiring.

 

[500e]

ACR15 was fitted to a lot of motors in the day light goes from ign SW live when on running to isolated bulb holder from there to 6.3 lucar in alt should have batt volts on wire if disconnected from alt

 

[500e]

 

[not done it yet]

If the warning lamp comes on when you ground the warning lamp wire at the alternator, then there is nothing wrong with the wiring.

Agreed. Simple first check.


Alternators are basically quite simple in operation. The only really clever bits are the regulators.

The indicator light is around 2W, so around 170mA. Resistance will be around 70 Ohms. Resistance of the rotor windings will be likely a bit over 12 Ohms (say 1A at maximum excitation?).

Indicator terminal to earth resistance is easily measured. If it is not of a value which appears sensible (like far too high - such that the indicator bulb is more than slightly dimmed, compared with when it is grounded), the problem is between the terminal and earth. What can be more simple?

Self exciting alternators require some residual magnetism in the rotor core. Resudual magnetism in the rotor means the minimum alternator output will be greater than one that loses all its magnetism when not energised.

All alternators are of similar simple construction, the stator windings being the most expensive individual part.

A comprehensive (good) repair kit, to me, would include slip rings (comm) and bearings, but less likely a regulator. The regulator is a non-wearing part (as is the diode pack, of course, but diodes are more likely to fail or be destroyed).

These old ACR alternators have a separate regulator - many (most?) small modern automotive ones actually include the regulator within the brush-gear moulding, I think.

 

[Newlands]

View attachment 348826

Thanks for that - really helpful as, (apart from the coil and distributor obviously!) it is very close to my setup, even down to the colour codes.
So, problem solved. The white wire from the indicator lamp that disappeared into the loom apparently does a U-turn, changes colour and reappears in the most inaccessible place behind the dash panel and sneaks off to the starter switch just about out of sight. It had fractured inside the insulated spade terminal. Cleaned the green corrosion off and crimped on a new spade and I now have a warning light brighter than I’ve ever seen before.
thanks for all the help - some very useful diagnostic tips which I’ve stored away for future use.