Atwood Water Heater - Diagnosis Thoughts?

Old-Biscuit wrote:
The Electric on/off switch and control circuit use 12V DC....hence the DC Relay that is used to trigger the 120V AC to element

So YES ....if the DC Relay is STUCK 'closed' the 120V AC is energizing the element even if the DC voltage is shut down.

TWO relays failing in 4.5 yrs is unusual....they are not a common fail point.
But does seem to be more issues recently with the DC Relay Component
Have seen two relays where the AC wiring as broken/separated from relay and NOT allow AC Voltage to element.
Must be some of that 'quality control' from component vendors :S

Simple $0.50 relay failing could make that water heater into a very dangerous heated vessel.
T-stat opens (140*F)......no shut down
ECO opens (180*F).........no shut down
T&P Relief Valve pops open (210*F)....hot water that flashes to steam blows out ---electric still energized/heating.
Water cools due to increased flow of cold water inlet so T&P closes only to pop back open and blow steam when water over heats
T&P Relief FAILS>>>>>>>>>>>. Pressure builds until something lets loose....fitting on water lines at WH Tank blowing steam inside RV



All Atwood combo units (electric/propane) since 2004 model/design change use the Combined DC control Circuit with DC Relay for electric side.

Replace that DC Relay ...then take some voltage measurements
Especially the AC Ripple.......using voltmeter set to AC Volts measure the DC Voltage. Anything AC Voltage on DC Circuits can cause issues/damages.
AC Ripple is from 'converter' capacitor failing.

Or just dumb luck with bad DC Relays