Suburban water heater won't shut off

[rgnprof]

I have a 6 gallon Suburban water heater - older model, maybe even original (1993).  It is a SW6D model with direct ignition and - I THINK - has had a 110v hot rod added on as it has what looks like aftermarket wiring and a thermostat added to the side of the tank (I have never used the electric much, if at all).  Has worked perfectly for the 10 years we've owned the rig but just this weekend I started having trouble with the thing shutting off.  I'm thinking a thermostat problem but I'm having trouble finding the right part.  I haven't let it get hot enough to trigger the hi limit switch (which I think kicks in at 180 degrees??)...

I just ordered this one : https://www.amazon.com/Suburban-SB232282-232282-Switch-Assembly/dp/B003G9FZHA/ref=sr_1_6?crid=2FORZMKH468XZ&dchild=1&keywords=suburban+232319+12v+thermostat+switch+assembly&qid=1601496430&sprefix=suburban+232319%2Caps%2C278&sr=8-6

But my old thermostat has Part # 160921 from the manual and looks like this :  https://www.amazon.com/Suburban-160921-Thermostat-by/dp/B01LRDGQCY/ref=sr_1_1_sspa?dchild=1&keywords=suburban+160921&qid=1601497303&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyRllZQU5OOTg1RU1KJmVuY3J5cHRlZElkPUEwMTU4NzUwR0hSQU05S1MyRk0wJmVuY3J5cHRlZEFkSWQ9QTA2MzMwOTIxQUZVTDBVTktNSTJMJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

While the high limit switch is part number 231461 and looks like this : https://www.amazon.com/Suburban-231461-Limit-Switch/dp/B003G9FWMI/ref=sr_1_1?dchild=1&keywords=suburban+231461&qid=1601497387&sr=8-1

I'm confused....I understand that parts are superceded etc, but I have 4 wires connected to my current set-up with the current parts that look like the last 2 above (Part #s 160921 and 231461). Not sure where the  other wires go...

Any thoughts?

Thanks,
ryan

 

[Henry J Fate]

I would need to look at the wiring diagram to confirm but off the top of my head.... Two wires are for the thermostat and high limit loop circuit and the others are for ignition and the gas valve.

 

[PancakeBill]

Do you have a voltmeter?  It sounds like the reg thermostat is not opening when it gets too temp.  The over limit won't open for a bit.

The easiest cheapest is to replace both the thermostats.  They seem to typically be wired in series, so both have to be closed for burner to ignite. 

 

[Rene T]

How are you going to mount the t stat so that is sits firmly against the side of the tank. Your original has studs and nuts. The one you ordered has nothing

 

[rgnprof]

I believe on the one I ordered there's a hole that a stud fits through (I am attaching a pic of my current set-up and you can see the nut that needs to be removed and that it is actually holding on a H shaped bracket).

I am also attaching the wiring diagram...

I was more concerned with connecting the wires to the newer ECO and Thermostat combo part...

And I do have a voltmeter - what ohms reading should I be getting - and when?

 

[Henry J Fate]

Looks like the new stat and hi limit will fit right in and the other wires are the ignition and gas valve?

The only thing that I noticed is that the current hi limit looks to be a manual reset? The new set up should reset automatically if it shuts down on hi limit.

 

[rgnprof]

It looks like the new combo stat/switch has only 2 spade connections - for 4 wires?? 

What am I missing?  I'm guessing that I don't need the wire connecting the switch and the stat (see wiring diagram) - right?  That's what the solid bar is doing in the new combo part...

I kind of answered my question - I think - as I wrote this.  ;D

 

[Henry J Fate]

The thermostat and hi limit are wired in series. Two spades is all thats needed. Basically what happens is the thermostat controls the heating probably somewhere around 130f. If the thermostat fails and does not shut off the heat, the high limit will turn it off which prevents a dangerous condition. The high limit is a safety feature.

Look carefully at the wiring diagram. It is important that the wiring sequence is followed. The module board is the brain of the gas circuit. The module board responds to the thermostat and opens/closes the gas valve and provides the spark to light the gas then a flame is verified telling the module board that it is OK to keep the gas flowing.

 

[X-Roughneck]

RV Forum Hitting on All Cylinders. 

This is what it is all about Folks.

Lending a Helping Hand to those in need.

JD

 

[rgnprof]

Thanks Henry!  Really appreciate the help.

One last question in regard to the wiring sequence - in looking at the pic of the new combo switch, which is the thermostat?  And what is that white tube?  This will probably be evident when the part arrives...but just making sure ahead of time that I know what I'm doing.

 

[Henry J Fate]

The white tube is a reset tube. The high limit requires a manual reset if the control thermostat fails and the high limit turns off the heat. I previously stated that the high limit would reset on its own but that statement was incorrect. The tube helps to prevent accidental touching of power connections if a reset is needed.

 

[Rene T]

Thanks Henry!  Really appreciate the help.

One last question in regard to the wiring sequence - in looking at the pic of the new combo switch, which is the thermostat?  And what is that white tube?  This will probably be evident when the part arrives...but just making sure ahead of time that I know what I'm doing.

That is a reset button

 

[rgnprof]

Perfect - thought that was the case...and that answers the wiring install concerns as well.

Thanks folks.

ryan

 

[Rene T]

Please let us know how you make out

 

[rgnprof]

Installed the new thermostat today and tried it out - seems to be working great.  Heater shut off, tested water and at 130F...

Things don't usually go this easy for me!!

Thanks for the help!
ryan

 

[Gary RV_Wizard]

And thank YOU for the feedback on the solution. It helps to know what worked!

 

[X-Roughneck]

Installed the new thermostat today and tried it out - seems to be working great.  Heater shut off, tested water and at 130F...

Things don't usually go this easy for me!!

Thanks for the help!
ryan

This place is 777 Lotto!

Glad it worked out for you.

Now, Roll on out to your Next Adventure my Friend.

JD