Here are some things to check out if you are having problems with your Atwood water heater (which is normally a very reliable appliance):

If you press the button to start your water heater, and it starts only to "flame out" a few seconds later, the burner tube may require cleaning and/or adjustment.

First, you may want to try adjusting the burner tube, especially if you are not getting a strong blue flame.   Just loosen the set screw and push or pull the burner tube as required.   Sometimes, adjustment is needed due to vibration.   I have also found that adjustment is needed when there is significant change in altitude.

Second, the burner tube may require cleaning as it frequently attracts spiders and dirt.   Clean it with a wire or brush - do not just use compressed air.

If your water heater appears to be completely "dead", perhaps the thermal cutoff diode needs to be replaced.   The thermal cutoff diode is used as a safety precaution to interrupt power to the circuit board in the event of overheating or a fire.   The circuit board controls the flow of LP, and no power to the circuit board means no LP flow which means your water heater will not start if the thermal cutoff diodes are faulty.   Several people have advised that these thermal diodes are available at Radio Shack, but I would just make sure that they will function as intended and not just get a regular diode.   Here is a picture of the thermal cutoff diodes in my 98 36T (6 gal water heater):

picture of thermal cutoff diode in water heater

You can test your thermal diodes with a simple VOM.   You should have dc continuity in one direction.

Before you replace your defective thermal diodes, you need to determine what caused them to fail.   A "flame reversal" of your burner is a likely cause....which is most likely caused by a dirty burner tube (see above).   Also, inspect the combustion area and the cumbustion air pathway and clean as necessary.

CAUTION: You are working with LP gas that can cause fire, explosion or asphysiation.   Seek qualified help if you are not sure of what you are doing!

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Submitted by Bob Cook