Sail switch in 1976 Duo-Therm how to?

Thanks for all the comments. The battery is brand new deep cycle off the shelf from Costco. I have a 7 amp solar panel that works that recharges the battery. The wiring looks to be a 8 gauge and looks very clean. There must be a bottleneck somewhere in the system. If the wiring is the same then the current should keep it tuning at the same rate. One of my problems is that all of the wiring seems buried and not easily accessible to do andy tracing. I tried pulling the unit out to see if I could examine and maybe clean it out but I can't even seem to budge it and it appears to but be built in place and I would have to disassemble all the woodwork to be able to see anything.I can't see any other fasteners locking it down in place The furnace seems to have had some rewiring done to it and looks a bit jury rigged and perhaps the gauge of wiring and the type of connections are not sufficient to carry the load. Who ever did the work must have had better access then what I have had so far. I have only found 1 screw holding the kick plate in place and I removed that but it is still locked in place.