power draw problem

what else has he fitted to the vehicle,?

Ray

Certainly sounds like the Starter is staying on, Spinning up but not engaging.

Once in an old truck I found same problem.
Next time after you start with a fully charged battery, remove the lugged lead to the starter solenoid, and insulate it, and let it hang.

GO do your thing, come back 1 hr later and test battery with a milti meter.

Should be a good indicator there is a problem with starter, or solenoid.

Cheers
Bucky

Hi Ray
To me it sounds like the diodes are shot in the alternator and they are shorting to earth and draining the battery. Easy to check disconnect the alternator and wait or put an ammeter in series with the charge wire to the battery and check what is happening. Let us know what you find

Greenant

If he has flattened a new battery in half an hour then this means a large current of 20 amps + must be being drawn all the time.

This is equivalent to a starter soleniod being always on.

Such a current will cause sparking when the +ve lead is taken off battery.

Just remove leads in turn and watch for sparking to stop.
i.e. it should spark when batt lead comes off/on -check - put lead back on then move to starter soleniod or anything else in the loop taking each off/on checking for spark.

Other than whats already mentioned, the only other thing i can think of is the glow plug relay is shorted closed.....