Hot water heater won’t shut off

[Richarad345]

New here….recent acquisition of used 2021 imagine 2800BH
We have previously owned TTs so not a complete newbie but it’s been a while
hot water heater is 6 gal gas/elec
sitting at home in driveway tank fired up gas just fine. But wouldn’t shut off. Water way too hot. Shut it down
assumed stat/eco
replaced
same result..
next assumption control board..replaced that too
nope..same thing, fires but won’t shut down

am I missing something?
don’t know what else to try
should be warranted but first trip planned and don’t want to mess with that if possible

have not tried electric mode.

thanks
Rich

[Jlawles2]

When it reaches temp, check the voltage to the control valves. They could be sticking open.

[Richarad345]

Thanks will check
however, when shut unit off at control panel; gas shuts off

is it possible to jumper across thermostat ( or pull lead ) can’t remember if stat is normal open or closed….to see if gas valve registers and closes

i suppose it’s possible I’ve got second bad stat or board

[RJAPCOK]

Thanks will check
however, when shut unit off at control panel; gas shuts off

is it possible to jumper across thermostat ( or pull lead ) can’t remember if stat is normal open or closed….to see if gas valve registers and closes

i suppose it’s possible I’ve got second bad stat or board

It is possible to have a second bad T-Stat, but the probability is low.

If I had this problem, this is what I would do:

1. Carefully remove one wire from the T-stat. Try the WH. It should not operate on either gas or electric.

2. Replace the wire and try the WH on gas. It should fire.

3. Allow it to run a few minutes, then with it running carefully remove the same wire from the T-stat. It should shut down.

4. Assuming all of this is functioning correctly. With both wires connected to the T-stat, fire up the WH and check the water temperature. If it goes much over 140 degrees F without shutting down, the T-stat is either bad, or not making good contact with the WH tank.

One last thing... if you have an Awood "XT" model, I believe it will have a 155 degree F T-stat. All other Electronic Ignition Atwoods have a 140 degree T-stat. I am not familiar with the "XT" model, but I understand it has a mixing valve on the back that controls water temperature by mixing cold water with the hot.

You didn't say what make water heater you have, but mine is an Atwood and all control circuits are easy to access so this would be a relatively easy process.

I hope this helps.

Bob

[Richarad345]

Thank you for your responses.
after testing here’s what I’ve found….
no run with lead off stat
stops running when lead pulled from stat
12vdc at gas valve(s) (running)
Low voltage across stat leads (running)

I may have been boy who cried wolf.
after several tries, i was wiggling leads at stat to try to get better shot at meter probe and tank shut off. Was afraid I had shorted something because i wasn’t expecting it.
water at lav at that point tested about 154-155

since stat was list as being rated at 60C (140F) I had been shutting off manually at around 150 before with the assumption that 10 over was out of tolerance

any event, it seems I have a working heater now. (I cycled several times)
with pretty hot water?

thanks again for advice
Rich