Did it ever work?
Since its a "new to you" unit, it could be something as simple as a wall switch that switches between two "high draw" appliances.
In my Flagstaff there is a 3-way wall switch low to the floor that switches between the microwave and the "fireplace" heater (and off). That keeps the total amp draw to 30 amps. In order to provide enough power for both at the same time would require a 50 amp service.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW