Hi Charlie,
Pull the receptacle and check to see if it is a "stab" terminal or screws. If it is "stab" replace it with a female rated for 20 amps.
I've replaced all but two of mine. I'm able to heat 100% electrically at -37 C (-34 f).
upsidedown Charlie wrote:
The receptacle closest to the front of the bus is safe to plug a 1500 watt heater into and that's the one we need to use. I can supplement heat with the portable and set the gas furnace to a lower temp and save gas. Winnie tech support has been very helpful.