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Topic: Atwood Water heater question (Read 955 times) previous topic - next topic

Atwood Water heater question

Hello Foretravel systems geniuses.  I need your help with my water heater.  Yesterday, the thing stopped working and we were just too busy in the day to mess with it, but today my hubby and I got out there to check out what was happening.  First off, we are dealing with an Atwood 10 gal gas/electric model GCH10A-4E.  When we turn the gas switch on, the green light came on, but the ignition didn't happen.  Nothing at all happened.  According to the manual, if a flame was not sensed a red light should have come on, but the red light never happened.  I checked the fuse, per the manual instruction and all was fine.  Then it said to check the thermal cutoff.  I looked and thought, 'Hm....not seeing this "thermal cutoff" that is clearly present in the manual.'  Anyways, being thoroughly confused as to why this thing would have any reason not to work, I came on here for help.  I found a thread where someone was having a similar problem and someone suggested they check the continuity of the current at the thermal cutoff and if that was ok to remove the large white connection at the circuit board and put it back in.  So, once again, I'm confused why I don't have this thermal cutoff.  So, I skipped the advice about the thermal cutoff and just removed and replaced the large connection at the circuit board.  Sure enough, when I flipped the remote switch, it lit right up and we now have hot water. Now my problem is, am I supposed to have this thermal cutoff like I am seeing in the manual diagrams and like I read about in the forums here?  It sounds like a safety feature and kinda important.  If so, why is it not there? I just have a regular old wire where it should be.  I do have documentation from the previous owner that states that the water heater has a 140 degree, factory set non adjustable temperature.  Would that be the reason why the thermal cutoff is not there? Or should I be getting on Amazon and purchasing one right away?  Thanks for any help you may be able to offer!
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!

Re: Atwood Water heater question

Reply #1 –
From what I remember, when I was looking for information when I had this issue, is the thermal cutoff is only important as a safety when running on propane so the current won't flow to the gas valve if there's an issue.  I think there is some other safety device in place when operating on electric. 

So, if you need to, just run on electric until you can get a couple of additional thermal cutoff devices.
Jennifer
2003 36' U295 (# 6070)
Thousand Oaks, CA

Re: Atwood Water heater question

Reply #2 –
Well, we are partially boondocking at the moment. My husband is providing interim work at a church and they are allowing us to stay in their parking lot and plug into 120V power outlet, so we can't really use the electric portion right now. 

So, I am assuming from your answer, that if we are using the gas option often, I really SHOULD have that on there.  Still not sure why it was removed then?  Maybe the previous owner didn't often use the gas, but why would he take it out.  I guess I could just ask him.  I just didn't want to bug him if it wasn't an issue.
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!

Re: Atwood Water heater question

Reply #3 –
Thermal cutoff is just a "temperature fuse", like any fuse, it has no function except to open the circuit if there is a problem.  Proper physical positon of the thermal fuse would put it in the path of a flame that is not contained into the heating tube.
With gas flames, if there is not proper gas pressure or not proper air being added to the burner, the flame may be weak and dance outside the burner, where it can melt wires or catch something on fire.
You could even have two thermal fuses in series one after the other to cover even more area.  Remove thermal fuse and use continuity meter setting to test to see if is ok.
Everything will work the same with thermal fuse in place or with thermal fuse missing from the circuit.

Re: Atwood Water heater question

Reply #4 –
Quote from: Barry & Cindy –
Thermal cutoff is just a "temperature fuse", like any fuse, it has no function except to open the circuit if there is a problem.  Proper physical positon of the thermal fuse would put it in the path of a flame that is not contained into the heating tube.
With gas flames, if there is not proper gas pressure or not proper air being added to the burner, the flame may be weak and dance outside the burner, where it can melt wires or catch something on fire.
You could even have two thermal fuses in series one after the other to cover even more area.  Remove thermal fuse and use continuity meter setting to test to see if is ok.
Everything will work the same with thermal fuse in place or with thermal fuse missing from the circuit.
Oh.....I see now.  Wow...I really should have that on there then!  I saw on amazon where I can get a kit of two for $15.  I should probably go ahead and get that.
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!

Re: Atwood Water heater question

Reply #5 –

Did you PM JOR and ask him about it?  I'm sure he would try to answer your question if he knows anything useful.

I don't think the fixed temp thermostat has anything to do with the thermal cutoff being absent.  I think it is more likely that at some point there was a problem with the thermal cutoff, and it was removed.  From the drawing in the manual that I found (online) it looks like the thermal cutoff is just a little jumper wire with a push-on connector at each end, and a diode in the wire.  It could easily be removed, and the power wire connected directly to the thermostat.

If you decide this safety device is indeed missing, then I would suggest you replace it.  Get it online, or most camping supply stores will probably have it in stock.

Amazon.com: Atwood 93866 Water Heater Thermal Cut-Off Kit: Automotive

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Atwood Water heater question

Reply #6 –

Yup.  That's the exact one that I was looking at.  I'm gonna go ahead and get it on the way.  I should have it in by Tuesday.  I will also put an email in to JOR to make sure there wasn't a reason it was like that. 

Quote from: Chuck & Jeannie –
Did you PM JOR and ask him about it?  I'm sure he would try to answer your question if he knows anything useful.

I don't think the fixed temp thermostat has anything to do with the thermal cutoff being absent.  I think it is more likely that at some point there was a problem with the thermal cutoff, and it was removed.  From the drawing in the manual that I found (online) it looks like the thermal cutoff is just a little jumper wire with a push-on connector at each end, and a diode in the wire.  It could easily be removed, and the power wire connected directly to the thermostat.

If you decide this safety device is indeed missing, then I would suggest you replace it.  Get it online, or most camping supply stores will probably have it in stock.

Amazon.com: Atwood 93866 Water Heater Thermal Cut-Off Kit: Automotive
As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!

Re: Atwood Water heater question

Reply #7 –
OK....Jor said he has no clue, that he never touched it and as far as he knows its factory.  There were two owners of this coach before him.  Maybe I will just call atwood and give them the model number and see if, for some reason, it was done differently on this model.
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!

Re: Atwood Water heater question

Reply #8 –
Does that wire that you see just connect directly to the right side of that right plug?  Or maybe you have a different setup?

In the pics below, you can see the thermal cutoff on the right side of the right plug, on the brown wire going up with the wire bundle going into the water heater. 
Jennifer
2003 36' U295 (# 6070)
Thousand Oaks, CA

Re: Atwood Water heater question

Reply #9 –
The "diode looking thing" is not a diode, but a thermal fuse, i.e., it will open the circuit if it gets too hot. Once it has opened, it has served its purpose and is trash. Barry provided a good explanation of the purpose. You can operate the water heater without the fuse, but it should be in place for safe operation.

On our previous coach, we blew about three thermal fuses on a single trip. After an RV shop in Billings, MT, flushed the dauber nests (mud nests) out of the flue, the water heater worked properly and never blew another fuse.

We have installed "dauber screens" on the furnaces and water heater on the FT.
J D Stevens
1997 U295 CAI 36' Build #5085
2002 Subaru Outback
Motorcade 16869
Bellville, TX

Re: Atwood Water heater question

Reply #10 –
J.D.,

I'm not picking a fight - I'm sure you know more about this stuff than I do.  The only reason I called it a "diode" was because that was what I read in the factory manual.  I guess they need better proof readers!

http://manuals.adventurerv.net/Atwood-Water-Heater-Service.pdf

Page 28, Water Heater Terminology, right hand column:

Thermal Cut-Off                    Heat sensing diode that cuts
                                                power to circuit board if a flame
                                                backs out of the burner tube or
                                                flue tube normally caused by an
                                                obstruction in these areas
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Atwood Water heater question

Reply #11 –
If this link works, here is a pic of what we have.  The thermal cutoff should be part of one of the brown wires, according to the manual.  If tho link doesn't work, I will have to upload a pic from my computer when I get home later.
https://scontent-ord1-1.xx.fbcdn.net/hphotos-xap1/t31.0-8/fr/cp0/e15/q65/12909454_10209494804155907_7005336962606293250_o.jpg?efg=eyJpIjoidCJ9
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!

Re: Atwood Water heater question

Reply #12 –
That looks very similar to the photos posted by Jennifer.  Appears that somebody just removed your thermal cutoff, and connected the brown wire directly to the right hand terminal.  Easy fix (you DO have Amazon Prime, right?).
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Atwood Water heater question

Reply #13 –
One of the confusions on Atwood propane heaters is the newer units with Atwood electric rear mounted heating element has a different control board and wiring sequence than the older style heater that many coaches have.  The older style has a 'standard' (& less expensive) control board and a simpler wiring sequence.  Since everyone assumes we are all talking about the same thing, we can get confused without knowing it.

The new board controls a rear-mounted 12-volt relay coil that turns on 120-volt current to heat probe, as well as controlling the propane system.  The older style control board only manages the propane system.

The thermal fuse may very well be diode based and stops current flow when sensing flame temps.

The following is from memory and is probably how it works:
Older units have 12-volts from inside heater switch going through thermal diode, then going through auto-reset emergency high-temp cutoff ECO switch that is pressed against the metal storage tank, then to board, so if either fuse is blown or ECO open the board sees no power.

New units have two 12-volt wires from inside heater switches going direct to board, one for electric & one for gas..  And the wire from the board that goes to the ECO should be removed at the ECO, and connected to the thermal fuse, and the other side of the thermal fuse should be connected to the ECO.  The ECO will now also shut off the 120-volt heating element similar to how the regular tank thermostat also turns off the 120-volt heating element.

I think the thermal fuse is sold as a quantity of 2 on a blister pack and is inexpensive, and using both in series may give you wider protection and easier longer wire positioning.  The thermal fuse used to be 'optional' and never installed.

We used to have the older style Atwood with 120-volt heating element externally controlled and installed the newer style with integrated 120-volt control a few years ago.

Re: Atwood Water heater question

Reply #14 –
So that explains it then, that they were optional.  I have already purchased the two pack on Amazon with my prime membership, which means it will be here Monday.  It never hurts to have extra safety measures.  If the WH hadn't gone out,I never woulda known I didn't have it and we probably would be just fine.  Its already survived 20 years without it.
Thanks for everyone's help.  You guys are awesome!
-Trent and Siobhan Walker + 5 boys
Proud owners of a 1995 U300 SE that we bought from Jor.  We are so blessed and loving life on the road!
 

Re: Atwood Water heater question

Reply #15 –
Sounds like you are on top of this one.  As for the original failure, a little dielectric grease on the contacts of the circuit board will help prevent it from happening again in the future.  The circuit board is essentially "outdoors" and the connections can develop surface corrosion.
John Fitzgerald
1991 U300 (SAI) Side Aisle Island Bed 40'
Detroit 6V92 with Allison Retarder
Meridian (Boise), Idaho