Atwood Water Heater only working on electric..

Monved from General RVing

Several possible reasons. But first let me ask you a question. Do other Propane devices work? You might be "out of gas" as it were. Or you may have turned the valve off on the tank, or your detector may have failed (if it controls a valve, some do some don't) or you may be low on 12 VDC.

Mine the control board failed, after many years..

Several other possible issues Some of which have already been reported
If you like I can give you my furnace boilerplate. it applies to Water Haters as well if you ignore blower and sail switch comments.
This document was created while I was diagnosing MY furnace.. I am told I missed one possible issue... Sadly I forget if I updated the document or not and the issue Bad connections anywhere along the line can lower voltage

When the T-Stat calls for heat the control board starts the blower (1)
The blower blows closing the sail switch (2)
The control board then opens the gas valve (3) and begins sparking (4.1)
Gas Flows (5) And ignitets (4.2)
The flame heats the flame sensor (5)
The flame sensor sends .480 volts to the control board (6)
which then detects the .480 and continues operation (*)
When the T-stat says "Enough already" (RV is now warm)
The control board shuts off the gas flow (*)
and then turns off the blower after a cool down (*)

*: At nearly every step the control board is involved. IF IT IS BAD, things will not work.. I recommend replacement boards from Dinosaur boards.. When Mine went out the Dino board was less than half the price and when opened the box the quality of construction and workmanship, and then design was very clear to my trained eyes.

1: No 12 volt to furnace, blower motor shot
2: Low 12 volt, air ducts clogged, blower "obstructed" bad sail switch
3: Bad solenoid, Clogged Gas Jet
4: .1: Bad ignition circuit (high voltage) on control board. .2: Points too wide (Very common it seems)
5: These do not often fail but they can
5: Bad connection, NOTE:
5 and * Bad wire.

* applies to all steps by the way So does bad wire/connection.

Clean the ground cable

JimR

Yup, first question is how far into the cycle it goes:

When someone turns it on, and you are standing outside by the water heater, do you hear/feel the gas valve "clicking" which provides propane to the burner?

Do you hear the clicking of the igniter?

Do you smell propane and/or does it try to light?

If it lights, how long before the flame goes out?

Thank you guys. Ill give this a try!!

DO you get a 'spark' from spark electrode when you turn it ON?
Does main flame attempt to light at all?

Your Atwood uses the SAME t-stats and circuits for electric & propane so that part of system is good if electric is heating.

Only part that is separate is the circuit from propane ON/OFF switch to circuit board and circuit board DC to spark electrode and gas valve

Circuit board has 2 push on connectors
Pull both, clean contact surface with pencil eraser and then make sure pins make good contact when you push connector back on
Pull spark electrode high tension wire from transformer on board. Make sure it makes clean/tight contact when you push it back on
Make sure spark electrode assembly screw is tight.....it provides ground
Spark electrode has to be 'engulfed' in main flame..tip red for 'flame proving'
Spark electrode should have a strong spark....very audible 'click'...if not check gap (1/8")

So does it spark......does main flame attempt??

Could be a spider web in the burner tube.

Make sure your igniter is clicking when the heater is turned on.