Hi Michael,
The s704 relay is usually used with the overvoltage detector from B&C. It is designed to disconnect the regulator output or alternator output in the event of an overvoltage. It crowbars a circuit breaker in the alternator switch cct to de-energise the relay and disconnect.
With your arrangement the relay still provides for an alternator/regulator disconnect, albeit manual. Generally you want stuff to fail open if there is smoke, i.e. not be powered off.
Not sure if you are using 2 separate toggle switches, but the use of the S700-2-10 dual gang switch allows you to power on the master, and connect the battery to the bus independent of the regulator supply in the middle position. With switch in the top position it connects the regulator output to the battery. This also prevents regulator output being applied directly to the bus without the battery in circuit, (some regulators go max output if no battery is in circuit)
Jeff modified his original 2006 aerovee circuit, when he built 1374
http://www.sonex604.com/misc/Sonex1374ElecSys_V1_15Sep13.pdfThis is almost exactly the same as how I've wired mine.
Anyway, I'm wondering if there is something funky with the regulator/rectifier?
I'd disconnect the regulator output and also isolate the rest of the circuitry as well by pulling out the 20A fuse and disconnecting the 4AWG to the starter.
This just leaves you with the 2 relays, the battery and the switches.
Check the operation of the switches and relays first up, and then add each connection back individually and check again.
If all good progressively add the regulator, 20A fuse, starter.
Cheers
Tony