1. I would replace it or at least pull it and see whether it will run wired direct to the battery. I have wires with alligator clips for such things. I should wire in a fuses but haven't.

The good blower ran easily. The bad stopped and wires got hot. I was using a 12v boat battery with the blower removed and set on 2x4s on the shop floor.

Your aux water pump is likely bad and cat ruin your push control. You can disconnect. My SD heat is sufficient with the pump disconnected and TN winters.

__________________
85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.