Dometic WH-6GEA does not work on electric alone

[Spindle]

I have a 2022 Forrest River Surveyor. It has the “dreaded” Dometic WH-6GEA water heater in it. It’s my understanding that this water heater is supposed to run on gas alone, electric alone or on both at the same time. Mine only works on gas alone or gas/electric together. Will not run on electric alone. It has the 4+6 pin connector. Bought the camper New so no one else but camping world has had their hands on it. I’m a Master Plumber with my own business, so I know my way around trouble shooting. I have 12v on the white wire coming from the switch for the electric. When the 6 pin plug is unplugged I have 12v to the pin for the yellow wire. Plug that plug back in and voltage goes away. If I turn the gas switch on my voltage comes back and will run gas and electric. Gas works fine by itself. I’ve had the thermal diode go bad and a circuit board. I’ve tried 3 other circuit boards and get the same results on all 3. Can not figure out why this water heater will not work on electric alone?

[CA_Traveler]

Sounds like you have high resistance on the 12V wire and meters draw almost no amps and will incorrectly indicate voltage when none exists with a load. Measure the 12V on the yellow wire with a load, sometimes a 12V auto test light is enough.

It sounds like you are describing a bad switch?