The access hole is on the lower backside of the backing plate.
It's oval so pry out the plug and shine a light in and look,there is a toothed wheel...
This was all done with just the switch on but with the car cold.Because there is a slight diff in volt readings when it's hot to cold.
I'm new to the site but I have read this on many other sites.
Well I checked mine and it was at 1.48v.Before I adjusted it wouldn't idle when cold...
It's not ruined.You could have them bore the stud holes out,it wont take much, to the 5.0 size and then install 5.0 studs.It'll be a lot cheaper too.