On Mon, 23 Apr 2018 08:53:44 +0100, Chris Bartram wrote:

On 22/04/2018 21:48, Jim K wrote:
[snip]

Shurely if it is an alternator there's no need for a separate
regulator as such?

(If a dynamo then there is)

An alternator with a failed (or none-existent) regulator will boil a
battery dry (and probably cook the electrics) in a very short order.

Depends on the failure mode. If the series pass power device used to
control the excitation current going to the field winding via the slip
rings goes short circuit or a fault elsewhere causes it to be turned
fully on, then yes, it'll boil the battery and cook the electrics. If it
fails open circuit or a fault elsewhere prevents it from passing
current, you'll get little to no charging current, depending on how much
residual magnetic flux there is in the rotor and the speed of the prime
mover (diesel engine in this case).

--
Johnny B Good