21BHE Dometic Water Heater Problems

[howson]

SC21BHE

OK, then 120vAC is not getting to the element assuming (based on your admittedly newbie multimeter skills) it was measured correctly.

Let's back up a second as I was thinking about this and the original post something struck me odd. What is meant (from the OP) - thermostat is getting power and sending power to board? How exactly was this determined? It almost reads like the thermostat for the furnace is being confused as being needed for the water heater? (It IS the water heater we're troubleshooting, right?)

Howard

[SC21BHE]

Hi howson we are talking about the water heater. I was told by the tech I spoke with that the TStat often goes, so we checked to be sure current was flowing to the TStat and from the TStat back to the board.

hope this clarifies my earlier info

[SC21BHE]

howson can you confirm from the diagram what the return for the yellow wire would be? I can test it tonight.

[howson]

howson can you confirm from the diagram what the return for the yellow wire would be? I can test it tonight.

On the diagram note that the metal case of the relay is the "ground", or as I prefer to state, the -12v return. So the black lead should be on the case of the relay and the red lead on the yellow wire where it connects to the relay. Obviously, the meter needs to be set to DC.

What should be read is the same DC voltage read across the other combinations already discussed when the water heater is being commanded to warm the water (electric switch is ON on the control panel).

If any of this input is questionable (to you), please STOP and ask questions or "raise the white flag" and hire a technician to troubleshoot.

If the relay has good DC voltage (at this time it's my understanding the element does not have 120vAC across it) then either there's a 120vAC supply issue to the relay or the output contacts on the relay are bad.

If looking at the diagram it's not obvious how to isolate the exact issue of the "missing" 120vAC, I again will state it's probably best at this point to hire a professional. Too easy to damage the RV or yourself with an errant probing of the DMM with live power--especially 120vAC. No shame if that's the course chosen. Keep in mind I've been doing this type of troubleshooting for >40 years on electronic/electrical equipment, so what's "easy" for me is not expected from those just getting started. (Ask me about my woes when working on the RV's plumbing and you'll understand.)

Howard

P.S. For the record, when the continuity test across BRN1 and BRN3 showed 0 ohms that meant the thermostat ("Fixed Temp Cont T-Stat) and "Thermal Cut-Off" are both good so they are not the problem. The statement "...so we checked to be sure current was flowing to the TStat and from the TStat back to the board" is still a bit fuzzy. How was the current measured? I doubt it was current. Much more likely it was voltage. Please realize this is not a "happy to glad" word interchange--there's a significant difference between amperage ("current") and voltage.

[ncitro]

SC21BHE On the electric side I can say the relay is common to fail. When I still had my Atwood/Dometic I used to carry a spare, I had two fail over three years. Mine took this relay:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[SC21BHE]

Thought I would circle back.. after a Dometic dealer looked at the trailer they determined the board to be the problem and replaced it.