10 gallon Atwood HWH Propane won't fire

[SFPD 226]

I have a 2003 Bounder with a 10 gallon Atwood w/h. It works fine on 110v but the lp (12v) won't lite. The spark element works fine but I have no gas. I have cleaned the contacts and checked the fusible link; all seem fine. I even bypassed the link; still won't work.

Is there a way to check the circuit board without replacing it or is there something else I should check??

My battery is fine. Plenty of lp. Gas stove works fine as well.

Thanks, John.

[Sammie]

John, Sometimes if your rig has sat a long time without being used there is a chance that the burner gas jet orfice could be plugged. I have seen an instance where a very small spider has built a web across the jet orfice and that has blocked the flow of propane gas needed for a flame. Pull the burner as a unit, then unscrew the jet and try to stick a very small wire or sewing needle through the hole. Hope this helps.

Sammie

[Gary RVRoamer]

In LP mode the circuit board triggers the igniter and applies 12v to the gas valve. If it does not sense heat at the igniter within about 15-20 seconds, it removes the voltage from the gas valve to shut off the flow. You can check fr 12v at the gas valve during the ignition cycle. If you have +12 and the igniter is sparking, your circuit board is fine.

[SFPD 226]

Gary, thanks for your response. I do not sense that the valve is opening at all (I smell no gas at all). Where do I check for the 12v coming to the valve and should it only be there when the igniter is actually sparking??

Thanks, John.

[nbounder]

Seems the world of water heaters is getting 'buggy' this time of year. (HARHARHAR).As was mentioned, during the sparking phase, the gas valve should have 12V and stay open to keep the flame on. If the flame sensor does not detect flame, the board will shut off gas, but flame should occur for a few seconds first. If you never get any flame, gas flow COULD be blocked by insects living in the orifice area - look closely! Or, the board is dead. Call Dinosaur for additional help, and if you need a board, get the plastic cover for an extra few bucks.

[Troubleshooter]

John,
On your Atwood water heater, you more than likely have a TCO (Thermal Cutoff) protection device that looks like a small fuse inside a clear plastic tube connected on one side to a brown wire, and on the other to a tab sticking out of a rubber cover on the front of the heater.
This TCO, if defective will prevent any voltage from getting to the gas valve, and thus prevent the heater from working on Propane.
To test it, use a Ohmmeter, and measure across the two ends of the device. A good one will measure near Zero Ohms. Another quick and dirty way to check if it is bad would be to simply remove it, and plug the brown wire directly to the tab on the heater. Then try the heater on propane. If it fires off now, you have found the culprit.
The tab I mentioned is one contact of the Fixed Temperature Control Thermostat. The other contact should have an additional brown wire going back to the control module. The thermostat can be tested with an Ohmmeter also. When cool, it should read near Zero Ohms, and when at the limit temperature, it would read a Open circuit, or Infinity Ohms.
There is a red wire from the module that goes to the ECO (Electrical Cut Off) switch, which then has a red wire to the gas valve. Again, it can be tested with an Ohmmeter. Normally it will read Zero Ohms. If it reads Infinity, then it would more than likely bad.
Any of the three are safety devices, and are needed for safe operation. The TCO is a common failure device, as it is a Temperature Operated Fuse, so to speak, and if there is a flashback from the burner, it will fail, thus shutting down the heater instantly. If yours is bad, I strongly recommend you replace it, rather than simply bypassing it. They are available from most RV parts places, and usually come in a pack of two.
I hope this information is of some use to you.


Bill
2002 Discovery 37T

[SFPD 226]

I bypassed the TCO and the result was the same. I found that there is no current going to the gas valve or the red wire that feeds it while the igniter is sparking which I am assuming means the board is dead??

John.

[NeilV]

Quote:

Originally Posted by SFPD 226 I bypassed the TCO and the result was the same. I found that there is no current going to the gas valve or the red wire that feeds it while the igniter is sparking which I am assuming means the board is dead?? John.

Maybe. Check the board for fuses verifying that they are good and making good contact. Also make sure you wait a few seconds after the ignitor starts sparking while checking for voltage at the gas valve as there can be a short delay between the ignitor engaging and the valve opening. I will sometimes use a 12 volt portable jump starter to apply 12 volts dc directly to the gas valve to check its operation. You will hear it snap open and closed. Shut the gas off and make no sparks if you do this test.

[Troubleshooter]

John,
Recommend you go to the following site and download the schematics. While they are not for your 10 gallon version, the wiring is the same.
Atwood WH Schematics
Since you say you have no voltage on the red wire going to the ECO Switch, lets back up.
First off, locate the green wire going to a screw on the chassis. This is the overall ground. Loosen the screw, and retighten it a couple of times, thus making sure you have a good ground.
Next, turn on the Remote Switch and measure for 12 Volts at the following places. 1. Brown Wire into and out of the TCO. +12V on both OK? 2. Brown wire out of Fixed Temp Thermostat. + 12V OK? 3. Red wire into and out of the ECO Switch OK?
If 1 and 2 are OK, but 3 is not, then you might have a bad module. If all three are OK, then you might have a bad gas solenoid valve.
Since you say you can hear the Ignition sparking, but no voltage on the Red wire, the module is suspect.

Bill

[SFPD 226]

All better now!! Replaced the circuit board and works like new. Thanks all for your help and suggestions.

John.