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Old 03-27-2016, 03:16 PM   #1
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Odd problem with Atwood water heater

I have an Atwood electric-ignition water heater that operates normally except for one strange issue: on the initial start in the morning the burner will start instantly (on the first spark or two) and burn normally for a second or two, then the gas solenoid will shut off. It will attempt an automatic re-light several times and timeout after three attempts (as is normal.) If I cycle power it will repeat the behavior and then eventually light off and run normally. Once the unit is warm it starts instantly and runs normally.

I don't think it is gas supply or burner adjustment because the burner always lights off right away and the flame is normal. I initially suspected the thermocouple but I don't think that is it since the solenoid shuts down almost instantly (even before a working thermocouple would register) and as mentioned, once the problem goes away (after the first cold start) the system works normally in all respects.

I have cleaned all contacts and connections, verified that the thermocouple is positioned in the flame, checked all the items in the service manual, etc., with no change in symptoms. About the only thing I am left with is the control board but before I replace that I wanted to get some opinions.

Thanks in advance...
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Old 03-27-2016, 03:27 PM   #2
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Mine was doing the same thing, and then one day it refused to light at all.
I too cleaned all the connections, gas tube, etc.
I replaced the board, it still did the same thing (sigh).
Finally I checked the ohms on the ECO (next to the thermostat) when it the heater was not lighting, no good, the ECO switch was open,but it should be closed at this point.
I tested by taking the leads off the ECO and connecting them to a fuse (not so much because I needed a fuse there, but because the fuse blades fit the wire connections perfectly).
Pushed the button and the heater fired right up, went inside and ordered a new ECO - problem solved.
So before you buy a board give the ECO a test to make sure it's working.
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Old 03-27-2016, 03:27 PM   #3
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Try disconnecting the LP supply hose and leave it off. Then disconnect the line from the LP tank. Blow a low pressure air through it, about 25 PSI or so. Have somebody watch the end at the heater, and see if any oil comes out.


I had this issue on a customers coach. I had to clean all the lines, there was oil in all of the lines. The oil comes from the LP gas, it's the smell that they mix in it, so we can smell it. After a while, or with some bad LP, a little oil can accumulate, and won't allow the gas to pass through. The LP is set at a very low pressure, around 1/2 PSI or so, it's not much. It's converted to 11" of water column, I think (it's been a while). Good luck
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Old 03-27-2016, 03:44 PM   #4
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Thanks for the suggestions. Since it is an easy test I will start with bypassing the ECO and see if that helps. I haven't had any problems with any other appliances so hopefully not contaminated lines but if it comes to it I'll give that a check too.
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Old 03-27-2016, 07:19 PM   #5
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Well I tried bypassing both the ECO and the thermostat but no change, drat. Good idea though.
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Old 03-28-2016, 06:03 AM   #6
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Darn, I was hoping that would work for you because that's a cheap and easy fix.
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Old 03-28-2016, 02:04 PM   #7
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Replace the igniter/sensor assembly. The rods for the assembly are held in place by ceramic beads. They develop very minute cracks and that bleeds off the sensor signal to the black control module. I used to have a trailer and had the same problem. Read this forum and others and was advised to replace the listed assembly. I was on a trip and replaced it. Didn't work. Finally made it home and went thru the whole thing again. Finally came to the conclusion that I had replaced a bad part with a bad part. Replaced the assembly AGAIN! It worked and is still working some 10 years later. Cost of the igniter/sensor assembly at the time was about $35.
Good luck, good health and safe travels!
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Old 03-28-2016, 03:57 PM   #8
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Quote:
Originally Posted by BeltoneMagoo View Post
Replace the igniter/sensor assembly. The rods for the assembly are held in place by ceramic beads. They develop very minute cracks and that bleeds off the sensor signal to the black control module. I used to have a trailer and had the same problem. Read this forum and others and was advised to replace the listed assembly. I was on a trip and replaced it. Didn't work. Finally made it home and went thru the whole thing again. Finally came to the conclusion that I had replaced a bad part with a bad part. Replaced the assembly AGAIN! It worked and is still working some 10 years later. Cost of the igniter/sensor assembly at the time was about $35.
Good luck, good health and safe travels!
This^^^^^

When heat is called for 12V DC goes to gas valve solenoids Opening them AT same time high voltage is sent to spark electrode. Gas valve solenoids only have 12V DC on them for 6-8 seconds------if a 'flame proven' signal is not received by control module the 12V DC is dropped to gas valve closing it.
3 attempts.no 'flame proven'---locks out ---whoch should give you a RED Fault light and in order to try again you have to turn ON/OFF Switch OFF then back ON

The 'flame proven' signal is generated by -flame ionization- of main flame and then sent back to control module via the spark electrode assembly.
Signal is only milivolt so doesn't take much to stop it: dirty electrode, loose ground, cracked ceramic, dirty connector/pins/contact on control module.

So good spark, good flame, spark electrode engulfed in main flame then milivolt signal being lost OR control module
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Old 03-28-2016, 05:09 PM   #9
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That sounds logical. The only thing that doesn't fit is the fact that the gas solenoid sometimes shuts down almost instantly, like 1 or 2 seconds. It should allow longer than that for a signal to be received from the sensor, and since it isn't I'm wondering if the sensor has anything to do with it.
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Old 03-28-2016, 07:57 PM   #10
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Don't know which manual you are using but try this one

http://http://beamalarm.com/Document...eshooting.html
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Old 03-28-2016, 08:35 PM   #11
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Quote:
Originally Posted by phays View Post
Don't know which manual you are using but try this one

http://http://beamalarm.com/Documents/atwood_water_heater_troubleshooting.html
Great reference, thanks.
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