Another water heater that won't light

[cathy624]

I have an Atwood 6 gallon water heater that froze over the winter. I removed it and had it tig welded, but now that I have reinstalled it, I can't get it to light. It goes through it's clicking stage, and the red light comes back on and stays on. The last time it was used was in December and it worked fine. How long should it take to purge the air out of the gas line? I have attempted to light it 20+ times. I'm getting nervous here.

[cathy624]

I took off the tube that covers the pilot hole, and was able to light the pilot light with a match while it was trying to self light. When it finished its electronic ignition cycle the pilot flame went out.

[HowieE]

Sounds like the thermocouple is not seeing the pilot flame or may be faulty itself. Take a look at the relationship between the pilot flame and the thermocouple. The flame should be engulfing the thermocouple and heating it. If this is not happening the gas valve will not have a proof of flame signal and will shut down as a safety. During the removal things may have been realigned.

There is a possibility the the thermocouple is bad but I would discount that as having happened just now.

Another thing that is happening now is stink bugs are making homes in the burner tube and cutting off the gas or causing strange flame patterns. Deon't sound like your problem but keep it in mind.

[cathy624]

Thanks for the reply. Is the thermocouple the white rod which sticks into the tank at the end of the burn tube? Wouldn't there first have to be a flame for the thermocouple to be the problem? I can't get the flame to light. If it is at the other end of the burn tube, how could it detect the pilot so far away? Hope this makes sense.

[HowieE]

My Bad.

Your unit is direct electronic ignition.

When the switch is in the ON position the ignition, that black box above the burner, sparks at the end of the burner and lights the gas.

Watch for sparks as someone turns the switch on.

If you have spark that the problem is a gas problem. First I would remove the burner tube and make sure it is clear of spiders or other things. If clear the next thing would be to check the 2 thermostats, red and brown wires just above and to the left of the burner. Remove the wires and check for continuity across each thermostat. In a cooled down situation both should be closed and react to an OHM meter. If one is open it is bad. Replace both they come as a set.

If you still have a problem it is time for a propane tech to get involved.

[cathy624]

We have confirmed we have a good strong spark. Thermostat looks fine. No blockage in the tube. It looks like it is a bad gas valve. Before I order a $100 valve I wanted to confirm power going to the valve. Should I be able to use the voltage meter on the red wire coming from the black box, and the ground screw on the black box to confirm power to the gas valve?

[HowieE]

Before buying a new valve.

remove the 2 red wires from the gas valve. While holding a volt meter on either of the red wires have someone turn the heater on. You should hear the spark sparking and should see 12 volts on the red wire. If you have voltage try the other red one and do the test again. If both red wires have voltage while the spark is trying the Black Box is OK. If you do not have voltage check the connections on those wires back to the Black Box and retest. If you still do not have voltage it looks like the control Black Box may be bad or the thermostat with the brown wires is not closed. Jumper the brown wires and try again. If you now have voltage the LOW thermostat with the brown wires is bad.

Now while the red wires are still off touch a 12 volt wire from the battery to one of the terminals that the red wires go to on the gas valve. You should hear a click. Touch the other terminal on the other side of the valve. Again you should hear a click. If both click the solenoids click the gas valve should be OK. This gas valve is a 2 chamber valve and both have to be open to pass gas. If you don't get a click from each side the valve may have a bad solenoid. Rare but possible.

Now for the real test. Now connect a wires to both terminals on the gas valve and while they are remote to the heater have someone touch, for a second, that wire to a 12 source. Again you should hear the valve click and you should smell gas at the gas tube. If you can get gas with this test and things above checked out go back and test the thermostat that the red wires go to. That stat should be closed while the heater is cool and show a reaction with an OHM meter across it with the wires off. If no connection replace the HIGH thermostat

This series should check the system. If all checks out OK I would again remove the burner tube and make sure it is clear of spider nests and or stink bugs.

[cathy624]

I cannot get a voltage reading from the red wires that hook up to the valve. I put the red lead of the meter in the connector of the red wire, and the black lead on the ground screw on the black box, and nothing registered on the meter.

Can I use a jumper wire from the brown power line wire inside the trailer to try both of the tests on the valve? I already have a jumper wire hooked up, and when I touched it to the terminals (one at a time) of the gas valve nothing happened. But I accidently touched it to the body of the valve and it sparked and the ignition started sparking.

[HowieE]

Yes the brown wire coming to the heater is battery 12 volts.

Are you saying you did not hear or feel either of the solenoid click when you applied 12 volts to each side. Make sure you have 12 volts on that wire and do it again. I can't imagine both side of the gas valve failing at the same time. It is not a loud click. The green wires to ground have to be hooked up from the gas valve to ground during this test.

You say you could not get a voltage reading on the end of either red wire coming from the High side thermostat. Was someone holding the heater switch on and did you have spark during that test. If the switch was off than there could not have been voltage on the red wires. If the switch was on and you had spark work your way back up the circuit. Check the other side of the High side thermostat. If there is voltage there the High side thermostat is open and bad. If you do not have voltage on the input side of the High thermostat check each of the brown wires, while removed from the Low side thermostat and the switch is on. If you don't have voltage on either brown wire while the switch is on I would say the Black Box is bad. If you have voltage on one of the wire note which one and hook them back to the thermostat and check for voltage on the other brown wire. If you don't see voltage on that wire the Low side thermostat is open and bad.

Voltage comes into the black box from the switch in the bathroom. When the switch is on voltage is applied to one of the brown wire and if the heater is cool that thermostat is closed and passes voltage back to the Black Box which in turn applies voltage to one side of the High side thermostat. That stat should be closed when the heater is cool and call for spark and gas. As the heater heats up the Low side thermostat will open and shut the heater off on temperature rise. If that stat failed in the closed position the High side stat will open and shut the heater off. It is a dual safety system.