Hot Water Heater won't shut off

[stringpicker]

My '97 Minnie hot water heater won't shut off. It lights and heats water fine but then won't shut off. I assume it's the thermostat. Is this likely and, if so, how difficult is it to replace the thermostat? Thanks.

[David Kanoy]

Stringpicker,

It is most likely the thermostat stuck closed, this happened to me the 1st year I had our used 2000 Winnebago.

If it's an Atwood, then the repair kit includes two replacement disk style thermostats and a piece of sticky foam material labeled ECO T'stat. On our 10 gallon Atwood the repair kit was part # A91447 and cost (several years ago) around $20.00. The parts are stocked at most dealers, Camping World, etc.

Be sure to turn of Gas/AC to the unit and clean the area on the tank under the old thermostats when you do the repair.

The "stock" Atwood thermostats are set to 140 degrees. There is also an adjustable thermostat replacement kit available if small children and scalding is a concern.

Hope this helps,

David Kanoy

[Clay L]

Both the thermostat and the high limit switch would have to be stuck closed. That's possible but is a very rare failure. The high limit switch is one of the two ECO disc switches mentioned by David above.


Is the relief valve spraying water out as it should be if the water temp/pressure is too high?

[North Of 49]

I'm curious to know how this turned out, stringpicker...?

I have the same problem with an Atwood tank... Flame doesn't shut off, and to Clay's point, it eventually it starts to release water though the pressure release valve (though very little amounts - steady dripping).

Can a person easily test these switches somehow?
Kerry.

[Roadking]

Q:::Can a person easily test these switches somehow? Yes... but it Depends on what you call easy. ---

When cold (i.e. below about 130 degrees F) both switches should have continuity and should pass the 12Volts DC that is applied to them via the water heater on/off switch. When they reach temp (140 degrees F for the T-STAT and 180 degrees F for the ECO) the switches should open and at that time the circuit board should close the propane valve and the flame should extinguish.

Given your heater never turns off it appears the switches (both the ECO and the T-stat) have failed in a closed position which is very dangerous.

Given your failure the easiest and safest way is to spend the $25.00 and replace the switches. If either switch fails, then both should be replaced.... they come in a pair and should be replaced as a pair just because if one failed is a closed position...then how long will it be before the other fails?? Not a risk worth taking.

Anyway...if you want to experiment you can test the switches...but you need to remove them...so why not replace them anyway.

You can test them by putting them in a small pot of water which is then heated on a stove. You only need about 1/8 inch of water and place the switch flat on the bottom. Use a cooking thermometer in the water and when the water temp reaches about 140 (plus or minus) a little you should be able to hear the disc pop on the T-stat. Carefully remove the very hot switch from the water and use an ohm/voltmeter to verify the T stat actually opens. After about 10-15 seconds the switch should cool enough to once again close.. showing continuity..

Continue to heat the water and around 180 Degrees F the ECO should "pop" and the switch circuit should open. As the switch cools it should close.
.
It is much easier and less risk to replace the switches

[North Of 49]

Stopped by an RV shop on Friday and grabbed the pair of switches (for $25, I agree that it wasn't worth messing around with the old ones to see if they were faulty). Installed them and same problem persists - fire doesn't shut off. Now, that said, I've left it for about 45 minutes and by that point in time there is water coming out of the pressure release valve (not fast - but very steady drips), so I assume something is not right. I have yet to take a temperature reading of the water after it's been running for 45 minutes - I'll try to do that in the next few days. If the water is higher than 180 degrees, I assume it's probable that there's something wrong with the control board (or if I'm lucky, maybe some bad wiring or a bad contact at the board)?

(PS - Thanks for the thorough directions, Roadking!!)

[DAN L]

Originally Posted by North Of 49

Stopped by an RV shop on Friday and grabbed the pair of switches (for $25, I agree that it wasn't worth messing around with the old ones to see if they were faulty). Installed them and same problem persists - fire doesn't shut off. Now, that said, I've left it for about 45 minutes and by that point in time there is water coming out of the pressure release valve (not fast - but very steady drips), so I assume something is not right. I have yet to take a temperature reading of the water after it's been running for 45 minutes - I'll try to do that in the next few days. If the water is higher than 180 degrees, I assume it's probable that there's something wrong with the control board (or if I'm lucky, maybe some bad wiring or a bad contact at the board)?

(PS - Thanks for the thorough directions, Roadking!!)

it could be the propane gas valve not closing when it should.

Water Heaters - Atwood Mobile

[bob109]

Originally Posted by DAN L

it could be the propane gas valve not closing when it should.

Water Heaters - Atwood Mobile

Here's a pic of the back side of the solenoid valve for the Atwood 10 Gal. Gas/ Electric Water Heater. You can see two solenoids with twin wiring. The valve operates on 12 volts. If you apply a 12v source to the valve you should be able to hear if it's opening and closing. When working, the front thermostat and ECO supply the voltage to the valve.

http://farm3.static.flickr.com/2020/...d0897617_b.jpg