Water heater troubles. Need input.

[Wdc7389]

Question about the Atwood propane water heater in a 1998 Safari 25. The unit has started malfunctioning in the following way: the burner ignites, but only burns for a few seconds before cutting off. This happens no matter how many times I repeat the ignition. Any ideas about how to go about a repair would be greatly appreciated.

[Silver Otter]

When that happened to us I went outside and pulled off all the electrical connections, brushed them with brass wool, put them back. It may be all mystical, but now the ignition works. If, on the other hand, you're not getting propane back there, try lighting the stove burners and letting them draw a bit, then try the water heater.

[Protagonist]

The most basic troubleshooting tips are:
1 - check the free-of-charge things first. Make sure there's no blockage in the air supply and/or propane supply to the burner before you look for a problem that costs money to fix.
2 - check the easy-to-fix things first. Cleaning electrical contacts as suggested by Silver Otter. A bad connection to the thermocouple could be the culprit since the thermocouple tells the unit when to turn on and shut off the heat.
3 - check the most likely problems first. If the propane won't stay lit, make sure you HAVE propane; an empty tank would cause the same problem.
Obviously you can only check one thing first, so pick which troubleshooting philosophy best matches your personality. But whichever you pick to do first, check the others as well. Only after you've done all of those should you look at mechanical defects like a bad thermostat that would cost money to fix.

[Wayward]

Assuming you've checked the obvious like propane supply and electrical connections, and your tank is cold when this is happening, it seems the symptoms are related to the thermocouple because the burner lights and then goes out.

Gas appliances have a thermocouple which is a simple sensor that sits near the flame. As long as it remains hot from the burner flame, this thermocouple allows the gas supply valve to stay open. So, should the flame blow out, the thermocouple cools off and signals the gas valve to shut the gas supply off.

However this thermocouple system must be temporarily "fooled" into thinking the burner flame is on in order for the water heater to fire up in the first place. That is the job of the ignition circuit.

Once the flame lights the thermocouple must get heat from the main burner very quickly or it shuts off the gas valve.

It could be a bad thermocouple, or a bad ignition control board depending upon the model of heater you have (or as mentioned above a loose/corroded connection).

If you are good with a volt/ohm meter you can download the manual for your model heater which usually has an igntion and valve circuit diagram. The thermocouple can be tested for resistance on/off an open flame like your stove or propane grill.

If not, you could use trial/error. First check all the obvious first as mentioned above. Look to see that the thermocouple is indeed sitting where it should be near the flame. If it still does not work, replace the thermocouple (probably cheapest), then try replacing the ignition circuit control board.

[A W Warn]

My WH had the same symptoms stated by the OP. After cleaning the electrical connections, running a brush through to make sure there was no intake or exhaust blockage, and cleaning the igniter, the symptoms persisted. I picked up a thermostat kit for about $20 at the local non-Airstream RV dealer. It took about 20 minutes to change both sensors and install the new cover. Only tools used were a flat screwdriver and pliers. Operation is back to normal now.

add edit:
The above is regarding my Excella.
Last summer I had similar symptoms on my Safari, in the middle of a camping trip. Both trailers have electronic ignition water heaters. This time it started requiring multiple switching to the on/off position until the WH would stay lit. Then it went dead one day while we were camping, during a heavy fog. Power was getting to the module and the fuse to the thermostat was good. Cleaning contacts did not help. The control module went bad so I chose to replace the whole WH. I think the module lost its seal and shorted out from moisture.

[AtomicNo13]

If your unit is a dsi model my money is on a failed control module. Atwood acknowledged a problem and used to replace these gratis. I had a few fail and when replaced never gave another minutes worth of trouble. The new version is encased in epoxy and has a fuse. The prior versions which fail do not.

[ventport]

I am betting on the thermocouple. If there is only one wire going to the burner area, the thermocouple is incorporated in the same sensor as the spark ignition. Also make sure the end of it is in the flame so it can sense the heat.

[Aage]

I always have to blow out the combustion tube (the large hole that passes through the tank) with compressed air. If I haven't used it in a while, I invariably get a small cloud of light grey soot which I have been told is burned cobwebs.

I use compressed air as is sold in computer supply stores in cans.

Hint: don't stand in from of the other end of the combustion tube; you might get a grey ring on your pants.

[Okiestreamer]

Call Atwood. Chances are they can and will help you diagnose the problem. They did for me.

[Jim in Pima]

Originally Posted by Wdc7389

Question about the Atwood propane water heater in a 1998 Safari 25. The unit has started malfunctioning in the following way: the burner ignites, but only burns for a few seconds before cutting off. This happens no matter how many times I repeat the ignition. Any ideas about how to go about a repair would be greatly appreciated.

Sounds like a bad thermocouple, or on newer models the spark gap,
this is used for flame sensing as well.
On St Simons right now playing weekend host at the Fort.