There should be a breaker for the Univolt, but not sure whether it would be in main breaker box or part of Univolt.. There is also (I believe) a rotary main cutoff switch located inside trailer (ours is behind foldout couch...) that cuts off all 12V
power, though may leave emergency brake circuit active... During the 80's, A/S also used regular wal switch mounted somewhere in trailer to switch beteen microwave and A/C outlets, since main circuit could only handle one or other. It may also be possible to drop power to Univolt by opening breaker circuit in ower box (usually at rear of trailer) where 110V enters. One circuit breaker there is dedicated to A/C and Microwave line, other may be feed to Univolt.
Glad to hear progress progressing... Sealer work and floor workable?