Battery switch failure?

[Saildanz]

Hi all, first post here....be nice!😉
I have an Endeavor 37 cruiser powered with a very experienced Perkins 4-108, the boat is new to me.
There is an extensive solar array and wind turbine going thru a Midnite controller to charge the house battery bank and an “echo charger” to keep the starter battery charged. Hi output Balmar alternator with its own outboard regulator charges both underway. After 4 hours motor sailing with both banks charged 100% to begin with, the starter wouldn’t crank and all circuitry was dead on house battery bank # 1 AND Engine battery #2. Oddly enough, the system was completely normal with a state of charge of 100% at 13.2v on Both position. How could this be? The battery switch is a Perko 8500 series switch with “1” “2”, “Both” and Off. It moves normally to all positions. Any ideas? Thanks for any assistance...

[GordMay]

Greetings and welcome aboard the CF, Saildanz.
Perform a continuity test, between the common post and (wach of) #1, #2, Both posts, with switch in each position.