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Wednesday, October 28, 2009

Water Heater Flame-Out

My water heater will light just fine. I light the pilot, turn it to the “on” position and the heater main burner lights. I have a nice blue flame. The problem is that the heater goes off in two to five minutes and does not heat the water. I had no problems the last time I used it before winterizing the motorhome.
Frank, (Brandon, FL)

 
Frank, I hate to be the one to ask this, but are you sure you placed the by-pass valves back into the correct positioning after de-winterizing? It sounds as if the cold inlet valve may be closed and the by-pass valve open or maybe partially opened. If so, the water heater will not adequately fill with water. It would still be possible to light the pilot and have the main burner ignite however. In this situation the temperature sensing probe (which is directly immersed in the water) would not "feel" the water getting hot since it protrudes into the tank and simply shut the gas control valve off. You're left with cold, by-pass water flowing through the hot side of the distribution system. 

First double-check the valve positioning of the by-pass plumbing. It's possible one or more of the valves may be faulty, I.E., not opening or closing fully. Then verify that indeed the water heater is filled properly. You’ll get free-flowing water out of every hot faucet in the coach when the tank has filled. 

One other possibility, although rare, is that the thermocouple or the electromagnet in the gas control valve may be faulty, thereby not holding the gas valve open long enough. I would recommend having the millivolt output of the thermocouple measured, making sure it produces a minimum of 12 or 13 millivolts. It's my recommendation to always measure thermocouple output while it is installed in the heater. Thermocouples are simple to replace if it proves faulty. If it's the magnet in the safety valve, then it's best to replace the entire gas control assembly. But I think I'd place my wager on one or more of the by-pass valves being faulty (or closed).

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