water heater lights but won't stay lit

UPDATE!!! The wire was burned off the spark probe. I found a RV parts dept at MB Thomas RV Sales in St. Louis that had the part. Replaced the part and fired up the water heater. Works like a charm. I have a hunch the wire was just bad enough that when the spark ignited the flame, the probe heated up enough to break the connection inside the probe and shut down the gas flow. Anyway, the main thing is DW is happy. Thanks for all your input.

Thumperpull wrote:
Well I took a look just now and the wire going into the back of the sensor that sits in the flame is OUT of the back where, I assume, it should be secure. Guess there is no choice now but to replace the parts????

If you get a spark, the sensor is good. Check the gap and make sure it is correct. It should be unless someone has got in there and monkeyed with it.

No need to replace parts yet. Make sure you are getting a good fit at the brass gas nozzle and the air mixer. This is where most problems are.

Also take the connectors off of the black box and clean everything you can reach with a pencil eraser. In fact, clean all every connector you can see. Tha black box rarely goes bad.

Well I took a look just now and the wire going into the back of the sensor that sits in the flame is OUT of the back where, I assume, it should be secure. Guess there is no choice now but to replace the parts????

OK. Thanks. I'll give it all a good look tomorrow. Maybe a little wire brushing with a small wire brush and tightening all mounting screws. Tonite it would light and burn blue for about 3-4 seconds then go out. Then it would try again in about 10-15 seconds. Over and over unti I figured it was a lost cause for now.

I've cleaned my thermocouple and blown out the tubing in the pilot area several times over the years. So far it's always worked with the camper water heater. But occasionally I've had to replace the thermocouple in space heaters in the house. They all stay lit, or not, using the same principle.

cross country wrote:
there is a sensor in the flame which must create the correct (voltage I think) to keep the gas valve open.......

The part you are referring to is the ignitor. It will spark igniting the gas. It, along with the flame then acts like a resistor in the system which then keeps the gas on.

The gap has to be to specs, all surfaces of the mounting need to be corrosion free and making good contact. Another serious area is where the brass gas nozzle meets up with the part that you adjust the gas/air mixture with. It is a slip fit and crud/rust can get between the brass and aluminum air mixer. It is part of the safety circuit and a few milli volts is present so if the slip joint isn't clean, it won't work

You can also clean the pilot assembly by used canned air ( available at Walmart, etc) that will help your pilot burn better and heat the thermocouple properly.

there is a sensor in the flame which must create the correct (voltage I think) to keep the gas valve open. This is a safety feature. It may be that the flame is not burning properly (blue as opposed to yellow) The thermocouple 1067D 2932052018 part numbers will not get hot enough to produce the required voltage. Carefully clean off any carbon from the sensor and position the sensor where the flame in the first moment is the hottest....usually at the tip of the flame.

If it was a house water heater I'd say its the thermocouple, but I don't know much about the water heaters in R/V's yet.