21BHE Dometic Water Heater Problems

[SC21BHE]

We have a 2022 21bhe with a dometic water heater. Earlier this year the electric water heater stopped working. We continued using propane, however it no longer works as well. I’ve spent an hour on the phone trouble shooting and testing with the dealerships mechanic.
- thermofuse is good (but we bypassed just in case)
- thermostat is getting power and sending power to board
- cleaned the igniter, no visible cracks and orifice is clear
- opened the bypass valve and water flows through it
- 2amp fuse is good; no breakers thrown; no dsi light on

On propane we’re getting an intermittent click and I could see the spark, however gas would not light. No smell of gas though (propane tanks are full and all other appliances work)

His conclusion was that the board was bad. I’ve replaced it and now I get a high pitch hum when I plug it in. On propane there is no intermittent spark; and nothing on electric works.

Looking for any suggestions on what is going on.

Thanks

[Country Campers]

SC21BHE

Usually when the electric side does not work that means the element is bad, have you replaced the element? Can you post a picture of the front of the water heater?

Brian

[SC21BHE]

Tested the continuity of the element and it was good.

[howson]

SC21BHE -- I'd look for a bad -12v return. I realize it's mentioned in the OP that "power is getting to the board" but where was the -12v return measured? It's very easy to get fooled by using a different "ground" point when using a multimeter.

My rationale is that both the propane and electric aren't working, so it's something in common. +12v has been ruled out, so that leaves the -12v return.

Definitely could be wrong, but it's where I'd start based on the documented troubleshooting to date.

Howard

[SC21BHE]

Thanks howson . If you’re referring to the power that comes from the TStat back to the board, it is > 12volts as well. If I misunderstood, let me know.

[SC21BHE]

Any other ideas?

[TedS]

This may help a little.

[howson]

SC21BHEWhen the voltage was checked, was the DMM's black lead on the negative pin on the board (green wires on Ted's diagram)?

[SC21BHE]

Thanks TedS and howson . I’ve retested using this diagram placing the red DMM lead on the orange wire (gas 12+) and the black DMM wire on the Green (12-) and still have >12volts. So no change whether I ground on the wire or the frame.

[Country Campers]

What is the exact voltage you are getting?

Brian

[SC21BHE]

Country Campers it ranges between 12.85 and 13.05.

[howson]

SC21BHE -- apologize for my slow responses. I won't bore you with the reasons, just know I'd normally be much more responsive.

Instead of trying to troubleshoot everything at once, let's (for now) ignore the propane side and focus on the electrical. Leave the gas REMOTE SWITCH off (for now).

Using the schematic posted by TedS , what are the following results?

With the (Electric) REMOTE SWITCH OFF, do a continuity test between BRN 1 and BRN 3. What is the result?

With the REMOTE SWITCH turned ON at the control panel, is there +12vDC on the board between WHITE 2 and GREEN 5? How about WHITE 2 and GREEN 6?

Assuming power is getting to the board through the REMOTE SWITCH, look for 12vDC across the RELAY (YELLOW 2 and it's RETURN connection).

Does the voltage at the relay drop to 0v when the REMOTE SWITCH (Electric) is turned OFF?

With the REMOTE SWITCH (for electric) OFF, what is the AC voltage across the element? (Remember to adjust your multimeter's settings!)

With the REMOTE SWITCH ON, what is the AC voltage across the element?

[SC21BHE]

howson that’s a lot for my meagre skills. Lol

1. Electric off - red DMM to BRN3 and black DMM to BRN1 = 00.1

2. Electric on - red DMM to White 2 and black DMM to White 6 = 13.53v …. red DMM to White 2 and black DMM to White 6 = 13.53v

3. I see the Yellow wire but can’t figure out what the “return” is?

4. Heating Element (Electric on) red DMM to Black and black DMM to Green = no register (I used 250v AC setting to test)

First time using a multi-meter

[SC21BHE]

I should add that it’s as if the unit is locked out. There is a high pitch hum coming from the board when I plug into the TStat, but no gas smell, no clicking, nothing.

[Country Campers]

Not sure if you have tried this yet but remove all power, shore power and disconnect the battery cable/cables. This should give you a hard reset incase the unit has locked out as you have mentioned.

Brian