1950s M series black out switch

[machelko]

Can anyone tell me if the M series main light switch can be operated under 12volt systems. I understand that the late model switch assembly had the circuit breaker inside and unsure if it works under 12v. I have a M135 that has unfortunately been converted to 12 volt. All lights work with 12 volt bulbs but the switch was bypassed with a toggle. I would like to return to original switch. I can get test light to power in and out but doesn't seem to operate lights. Any help would be great.