The PV diodes are on Engine MUX. That is why motor lead power goes to it as input. If lights work, the PV is not bad. He is equating burned wick to some damage to a board. Not the case. Run smoke dry, it burns wick. Have a fan failure, wick will burn. Loose impeller too.
Clearly something in engine though is running the 5V power supply near max output to cause the clicking and shutdown. Smoke fan is #1 suspect. But could be damaged wire harness too. Hard to say, but I have seen some butcher jobs done on the mux and such. Even on repairs where some one turns the tender into an upgrade tender but leaves the mux wiring in. Lighting and smoke don't like that. G