Tractor Alternator

plenty - if you don't mind opening it up a bit and putting  the alternator on the bench a full diagnosis is possibke. You will need a voltmeter, an ohm meter, an ammeter a source of voltage to act as a 'battery'  and a series indicator lamp for initial excitation, and eventually  the ability to turn the thing for testing. A power drill can sometimes be pressed into service.
Is it the sort with the regulator built in  or in an external box. ?

The external reg tyoe you can energize the rotor externally and see if it then generates or if the rotor draws no current, look at the brushes and slip rings. The built in reg sort usuallly needs the end cover to come off to separate them

If you have a photo of the thing, it will speed up the explanation.
M

Thanks Mike, at least you didn't suggest an oscilloscope! 

I'll take it off tomorrow and have a poke about. Yeah it's built in.

It's a compact tractor with a loader so it is unbelieveably fiddly. I nearly had a nervous breakdown changing the oil filter.

Thanks again.

well if you do have a scope it can be instructive, but it's probably overkill.

Mike.

well if you do have a scope it can be instructive, but it's probably overkill.

Mike.