Help... water heater won't light

mojospeople · April 08, 2017, 01:49:56 PM

It worked on our last outing but now no ignition. Actually it has randomly lit a couple times but doesn't stay lit and can't get it to start. It's really weird. Checked gas, flipped the breaker switch, unplugged ans plugged back in at the unit (under a rubber boot) to no avail. Thoughts?

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charliem · April 08, 2017, 02:46:32 PM

Sounds like the thermocouple or ignitor itself. The ignitor provides the spark to light the burner but the thermocouple keeps the gas valve open after a short preset time. Both have to work for a continued burn. Try having someone go outside and light the burner with a long match while the ignition cycle is happening. If it lights and stays lit it points to electronic ignitor. If it lights but goes out within seconds it points to the thermocouple. Both are easily replaceable. I assume you have cleaned everything and checked ignitor alignment. The circuit breaker has no effect on the gas operation but the WH must have a good source of 12 VDC and you should have a battery in place.

DavidM · April 08, 2017, 04:39:58 PM

In addition to Charlie's excellent advice (I almost always agree with Charlie) make sure that the ignitor is positioned so it makes a strong spark in the gas path. The ignitor element can be bent to do this.

Do the same with the thermocouple sensing element. It has to be positioned in the blue part of the flame to work.

David

mojospeople · April 08, 2017, 04:45:23 PM

So it isn't trying to ignite except about 3 times and was successful then but only ran for about 10 minutes (timed once) and obviously the water isn't hit yet. I could understand the thermocouple but not the random ignition attempt. Battery is at full charge. Also there are marked fuses and breaker for the hwh.

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charliem · April 08, 2017, 05:00:55 PM

I'm a little unclear from your description. If it lights within the 3 attempts but goes out after 10 minutes it could still be the thermocouple. It could be intermittant, close to complete failure, and just quitting after 10 minutes in the heat. Running 10 minutes pretty well exonerates the ignitor. It could also be the propane regulator producing a marginal flow. There have been cases of faulty regulators. I suppose it could also be the WH thermostat trying to cut off at a low temperature. Not sure how that would happen but failure modes are sneaky. When it goes out (10 minutes, water is cold)) does it try to relight almost immediately?

charliem · April 08, 2017, 05:27:10 PM

The WH fuse supplies the 12V circuitry and must be good for anything to happen. The breaker is only for the 120V side and has no effect on propane operation.

mojospeople · April 08, 2017, 05:30:18 PM

No it doesn't try to relight. It doesn't try to to ignite when I turn on the switch and then an hour later, boom. It ignites, burns for 10 minutes and shuts off. Attempts to light again fail. Wondering about gas pressure. I have a true connectors on the tank running to a camp stove.

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charliem · April 08, 2017, 05:46:34 PM

Sure acts like a thermostat. Are you sure the HW is not hot? Seems strange that it would not try to reignite. If the themocouple shut down the gas valve the thermostat should sill call for heat and the control board should attempt reignition. Same thing if gas pressure were low. It points to the thermostat for me. When the burner quits after 10 minutes try flushing the WH with cold water (just hook up a hose and run lots of water from the tap) and see if it will try to ignite. Or you could open the gray water dump drain and let a HW faucet run. The burner should run continuously attempting to heat the water. There are two thermostats on the gas side and two more on the electric side. One on each side is set for 130F and the other somewhat higher as a safety. There are reset buttons on all; make sure they are pushed in.

charliem · April 08, 2017, 05:51:38 PM

Have you tried it on 120V ? Does the water get hot or just warm?

mojospeople · April 08, 2017, 06:34:50 PM

We're currently plugged into 30 amp. Testing will have to occur at home to more. It really doesn't make sense sense. I'm thinking it's either the ignitor alone or in conjunction with the thermostat.

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charliem · April 08, 2017, 06:46:18 PM

If the WH shuts down after 10 minutes, does not try to reignite, but fires up an hour later it sounds like all is working fine. I'm wondering if the WH is really heating properly and satisfying the thermostat but the WH bypass valves are set improperly giving you the impression the water is not hot. If you're plugged into 30A the electric side of the WH should work fine and you should get HOT water.

mojospeople · April 08, 2017, 06:48:03 PM

Checking my bypasses next.

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mojospeople · April 08, 2017, 06:58:42 PM

Bingo! Forgot to close the middle bypass valve so cold was mixing with the hot, thermostat keeps it from lighting and the random light isn't when the tank drops below temp. Thanks! I can take a shower now!

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mojospeople · April 08, 2017, 07:00:08 PM

*is when the tank temp drops.

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Merlin · April 08, 2017, 10:58:17 PM

Quote from: charliem on April 08, 2017, 06:46:18 PM
If the WH shuts down after 10 minutes, does not try to reignite, but fires up an hour later it sounds like all is working fine. I'm wondering if the WH is really heating properly and satisfying the thermostat but the WH bypass valves are set improperly giving you the impression the water is not hot. If you're plugged into 30A the electric side of the WH should work fine and you should get HOT water.

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