While I was traveling last week, my wife ran into issues with our 15-month-old hot water heater; the pilot light would not stay lit. She managed to re-light it and got hot water for a single use but it went out again. Upon my return, we once again faced cold water. We turned to the Internet to try and diagnose the issue and found that if a pilot would light, but not stay lit, it could be 3 potential issues:

1. A bad thermocouple which is a unit that senses when no pilot heat exists and sends a signal to the thermostat to shut the gas off.
2. Dust, dirt, residue build up on the flame arrestor plate or burners
3. Poor air flow and/or gas pressure.

We first tried the simplest to fix, #2. We took off the outside door to the pilot and then carefully removed the inside door (right, then left side) making sure not to damage the cotton-like gasket. We made note of where all the lines went and used wrenches to remove the pilot line, main gas line and thermocouple line. We also removed the two electrical wires from the tabs on the outside of the inner door.

After everything was disassembled and both the right and left inner doors removed, I pulled out the burner and pilot unit (one piece). Everything was very clean but I took a wire brush and vacuum to it just in case. I re-installed everything and tried to light the pilot only to have more problems.

Now when depressing the red reset button and clicking the piezo-electric igniter, the pilot would light but even after holding it for 60 seconds, the pilot would go out immediately if I let go of the red button. This was one of the signs of a bad thermocouple. This wasn’t happening before I tried the cleaning, however. We reluctantly went to Lowe’s (Home Depot didn’t have one in stock) and bought a thermocouple for $6.97. The unit has good instructions w/ pictures so I’ll spare you the details.

I removed the inner doors again and removed the old thermocouple and installed a new one. After putting everything back together I tried to light the pilot and same issue. We noticed that every instruction whether online or in print noted DO NOT OVER TIGHTEN and one noted tighten to hand tight, then use wrench for 1/4 turn more. As a last-ditch effort, Jamie suggested to loosen the lines and then re-tighten by hand and barely tighten with the wrench - it worked!

We tested the hot water heater and even turned on the furnace to check if the pilot would blow out or gas levels would decrease and all was well. This is one of those cases where if I’m in hot water, that’s a good thing. Lesson learned that the sensors are very sensitive so try different levels of tightness of the lines before throwing in the towel.

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This entry was posted on Sunday, September 23rd, 2007 at 4:59 pm and is filed under Home, Knowledge. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site. This post has been viewed 2,020 times.