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?

[dougrainer]

ktmrfs wrote:
micro air thermostat will solve the problem. you can set it to ONLY use the gas heat if you want.

I think you are posting on the wrong thread:)

[Spindle]

Got it figured out. The switches were wired completely wrong from factory creating a ground loop. It works as it should now. Thanks

[ktmrfs]

micro air thermostat will solve the problem. you can set it to ONLY use the gas heat if you want.

[wa8yxm]

Ok yes it should work on Gas or Electric or both
now there are indicator lights. Either in the switch or near them for Gas and Electric. Does the light for Electric come on? (if not use a test light or volt-meter.. On my RV the light did not work...because the bulb burned out.. I installed an LED indicator. that worked and was not nearly as annoying (Bright)

No if the light comes on.. Next stop is a black box on the "Back"side of the water heater(Inside the RV) it should be fed by a ROMEX cable.. got 120 VAC..NO. problem found YES.. Look for 12 volt to the relay.. Got 12 v to the relay>> Did it close (if not problem found) Follow the wires from the relay to the heat element... Good chance a resistance check will show open circuit (should be around 10 ohms give or take a couple)

Suggested if it's the element get a 1500 watt 240 volt element .. this will drop the heater's current from 12.5 amps to 3.125 and help to prevent the click of darkness on 30 amp sites.. Takes a bit longer to heat but .. not normally a problem if you need how that fast.. Add gas.

[Spindle]

Basically the electric switch had the load wire hooked to the ground terminal and the other 2 terminals both had 12v feeds on them. Causing a loop while under load and that’s why my voltage disappeared. Crazy

[Spindle]

Doug. That’s exactly what was wrong the switch for the gas was wired correctly but the switch for the electric part was wired all jacked up. It had a jumper wire for power coming fro
The gas switch but was connected to the load terminal on the switch. It had another jumper wire coming from the power for the water pump switch going to the power terminal and then the actual load terminal had the white wire going to the water heater that is supposed to supply power to the board from that switch, but that terminal is the ground terminal for the light. The way I figured this out was to run a wire from the water heater back into where the switches are so I could figure out which wire was my feed wire to the switch. Re wired the electrical switch correctly and it all works like it’s supposed to now. Wired completely wrong from the factory. They caused a ground loop and that’s what I was reading with my meter and not supply voltage. Gotta love it. Thanks guys, you all really did give good advice.

[dougrainer]

Spindle wrote:
Yes 120v is present. The problem is that the 12v doesn’t go to the relay by way of the yellow wire when the electric switch is on by itself. For the electric to work the gas switch has to be on. It will run gas/electric and gas alone not electric alone.

Your wall switch is miswired. Disconnect the white wire. Cut it a few inches from the control board. Supply 12 volts to the wire coming out of the control board. You should have 12 volts on the yellow wire. It may be as simple as the 2- 12 volt switched wires from the wall switch are reversed. Doug

[Spindle]

Yes 120v is present. The problem is that the 12v doesn’t go to the relay by way of the yellow wire when the electric switch is on by itself. For the electric to work the gas switch has to be on. It will run gas/electric and gas alone not electric alone.

[dougrainer]

So, what about the orange wire? Doug

ARE you positive the 2 green wires have GOOD chassis ground.

[dougrainer]

When you turn on the Electric ONLY switch, The YELLOW wire should now have 12 volts. THAT wire goes to the 120 element 12 volt relay to close it and supply 120 power to the 120 element. IF NOT, then either the RV installed electrical wiring from the inside switch is miswired or your circuit board is defective.
The WHITE wire should have 12 volts when electric switch is ON, IF the control board is good, then the yellow wire should now have 12 volts. IF NOT, your circuit board is bad.The ORANGE wire should have 12 volts when Gas switch is ON. Yes, you can have both gas and 120 on at the same time. Doug

[Roger10378]

I am not familiar with that particular model but most of them work basically the same.

Electric heating is 115 Volt AC but you don't even mention checking for it. 12 volt is for control of the gas so if gas only is working you know the 12 volt is good.

You either have tripped the breaker for the 115 volt or there may be a switch on the unit. Or the electric might have been on with no water and burned out the element.

[Spindle]

The electrical switch supplies power (no ope circuit). The gas switch supplies power ( no open circuit) everything has power till the 6 pin connector is plugged in. It is actually more of a sign of a ground fault through the board but can’t find where it’s going. I’ve tried 3 different boards and all have the same issues. All the wires, let me say that again, all the wires have the power they are supposed to have with the 6 pin unplugged

[CA_Traveler]

Spindle wrote:
Unplug the 6 pin plug and check for voltage and the white wire has 12.5 volts, plugged the six pin plug back in and that voltage goes away.

That's the classic example of a high resistance (an open for practical use) connection.

[Spindle]

Not sure if it was clear or not. Electric works as long as gas switch is on. Turn electric switch off with gas switch still on and the electric shuts off. Turn gas switch off with electric switch still on and electric stops working. Unplug the 6 pin plug and check for voltage and the white wire has 12.5 volts, plugged the six pin plug back in and that voltage goes away.