Yo Steve.
Seems I had a bit of a BrainFart.
The only manual I have is for a Type 4, not a 3. Which isn't much good.
Because good old BR played a fast one on me the blighters, and things aren't what I thought they were. I was given a lovely green plastic bound cover labelled "Train Crew manual - Class 37 Refurbished Locomotives". But underneath in much smaller writing it says Drivers Fault Finding Data. I hadn't noticed that.
So I'd hoped it was a book saying how everything worked, and what was connected to what, whereas it's actually what we nowadays call a Matrix. It's full of schematics showing 10 things to do when the Blue Light comes on.
So not any help, sorry.
If it's any consolation, I'm pretty sure the controller on the 37 is a 4-notch type though, like most UK diseasals.
I do also have a book called The BR Diesel Engine Driver's book. It tends not to be too specific, and shows diagrams of 'a typical generator' rather than being specific, but I can have a search through it and see if I can glean any details.
In fact it will be a nice little project as the WX here has turned cold at last. I can break open the Bells and sit down for a long read.
And at least we've had the Solstice now, so we'll be climbing slowly back towards longer days slowly.
Anyhoo keep the Bodgie Budgie safe,
John