Old Skool Battery / Alternator question

[11ford11]

Take alternator off and get local auto electrician to check it out in test bench

[Citroënbender]

They're not exactly a commonly used rig now, most tradies just replace an alternator and if it's duff they get another under warranty from JAS, Cooldrive etc.

I've used the tester in my mate's workshop and it's only a basic one that reads output under a small fixed load, but nobody else even touches it.

[Crazy Dazz]

something somebody said above, whilst an old-wives tale, got me thinking.
Especially after I looked at that bright shiny near-new alternator.

Alternators require a field voltage, which is initially set by the battery or the ECU. Once running its either set by the ECU or the internal regulator, depending on the age and sophistication of the vehicle. (TBH in this car I'm not quite sure. Certainly the Petrol or the EFI diesel would have an ECU. This engine obviously doesn't, but may have a module performing some of the same functions.
In the absence of an external field voltage, alternators should provide their own via a diode. But I would guess that it starts low??

TBH, I'm not 100% sure of all the details (My one unit of electrical engineering was 35 years ago) and it varies between differing types. Point is, if there's something wrong with the field voltage, its not going to generate the current voltage.
So I tested it again, 10.5 V (ie less than the battery)
So I pulled out the plug that supplied the field voltage, gave it a shake, put in back in, pushed hard. Tested again, and we're back at 14V.

I'm hoping its just that plug.
I'll pull it again tomorrow, give it a good clean, and see if I can make it tighter.
At the very least I want to eliminate that as a source of problem.
I'll also try to check the field voltage being supplied.

[Crazy Dazz]

Ok, so found the box, and it turns out the near-new alternator is actually an Auto 8.

Further playing with the plug has produced no improvement. The field voltage tests ok.

Just seems the alternator isn't putting out enough.