If both the furnace and water heater quit at the same time, I would look for something that is common to both. In other words, I would not look at the sail switch on the furnace. Possible but not probable. I do not know enough about the specifics of both the furnace and water heater to diagnose for you, but I bet others here on this forum do. Good luck.
1993 Gulfstream Sun Voyager DP 30'
200 HP Cummins B5.9, 4sp Allison AT542
Toad 1998 Honda CRV, 2006 Honda CRV
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