Wouldn't It Rot Yer Boots - an off topic car problem

My old hilux has started to get a flat battery - sometimes.
I stuck an ammeter in the battery lead the other day and there was a 2.2 amp leakage current with everything turned off. I noticed a click noise each time i connected/disconnected the battery and hunted it down to the external alternator voltage regulator. Left the battery disconnected for a couple of days.

Today I started the engine up and when i turned it off there's no clicking or leakage current when I connected/disconnected the battery after running the engine -- bugger.

I was going to send it off to the autoelec's which pisses me off cos I was an autoelec before Noah started wearing nappies and cars have changed lots since then. If I had a wiring diagram I'd probably find the problem.
At the moment I reckon it might be any of
1. wiring fault
2. regulator fault
3. alternator fault
4. Bodgy ignition switch
5. Defective engine/start etc relay.
or some other confounded thing.

Trouble is intermittent electrical faults are a major pita to diagnose then repair and can cost lotsa loot for simple repairs. At the moment I'm disconnecting the battery when I stop the engine.

So has anyone with a hilux or any autoelec got a suggestion
Regards