I’ve never heard of either being used. Probably not enough heat generated.
But, O Frabjous Day, when I went out back the latch was working again! I have no idea what the problem was, or how it fixed itself. (Wasn’t the heat, as it was about -26 when I tried it again.) May have been the ground shifting from the cold.
And I was able to pull the two broken Ground pins out of the outlet by my car, so I can plug in the block heater again! Double Frabjous!
Temp is down to -33C. Projected low is -40 tonight. (I’m not staying up to monitor it.). Put the back bathroom tap on “drip” mode and hope that prevents freeze-up.