It’s Always Something

I ran out of hot water yesterday. Checked the heater, and the pilot was out. Relit it (piezoelectric igniter), and it wouldn’t stay lit. So I went to Home Depot and got a new thermocouple. After I replaced it, now it won’t light. So, either igniter, or not getting gas (neither of which should be the result of changing a thermocouple).


[Update a couple minutes later]

OK, I’m seeing a spark when I hit the button. Hoping that maybe I just have to clear some air out of the pilot line from when I removed the assembly to replace the thermocouple.

[Update a few more minutes later]

Disconnected the pilot line, definitely gas coming out of the valve. All I can think is that I clogged it somehow when I changed out the thermocouple. I’ll try inspecting and cleaning it.

[Update a couple minutes later]

I can blow through the line, but there’s a lot of resistance. Don’t know if that’s normal, or if it’s too much for the gas pressure to overcome.

[Update a few minutes later]

When I hook the line back up, and open the pilot valve, I can faintly smell gas at the tip, but I don’t hear a flow. It’s more like seeping, and probably not enough to sustain a flame. Not sure where the problem is, though. Might see if I can just replace it.

[Update a while later]

Took it apart, put it back together, tested it outside the unit, and saw a pilot flame. Put it back in and didn’t see much, but there was a dim light in there. I turned the heater on, and apparently there was sufficient pilot to make it work. It was probably working before, and I just hadn’t realized it…

6 thoughts on “It’s Always Something”

  1. Glad you got it going, Rand. The virtues of cold showers are vastly overrated.

    Man, who knew combustion could be so complex? Uh, wait, this blog is a place for discussions about (among other things) the launch industry 🙂

    1. Cold showers are great. Especially during the cold months. They build strength, toughness and endurance. But I may just be a weird outlier.

  2. Rand, in this case Safe is Indeed an Option. I work on all manners of “systems” in my house and car, but fossil-fuel combustion devices, I call someone.

    With natural gas, there is not simply a fire risk, not just a risk of carbon monoxide poisoning, there is a risk of explosion. Can you get someone to your house to at least inspect it?

    Is the concern that they will want to condemn your water heater? Just buy a new water heater — they are not that expensive and on account of hard water and corrosion, that don’t last all that long.

    1. I don’t see a need to inspect a water heater because a thermocouple needed replacing. This is a pretty standard procedure. And I have a CO detector.

      1. Good job DIY-ing it, Rand.

        I had a similar issue a few months ago with the pilot light flame detector on a gas furnace. While waiting for a new one to arrive, I tried a tip I saw online of cleaning the old one with fine steel wool — despite it not looking at all fouled — and that did the trick! I still haven’t decided if I should change out the now-working, old flame detector.

  3. Sounds like there may have been dirt or gunk in the pilot line. A pilot flame is generally on the order of 1/4″ to 1/2″ high on standby, 1″ to 2″ high (to activate the thermocouple and thus the main jet) when the thermostat calls for heat. If there’s a partial blockage and a too-small pilot flame, a brand-new thermocouple, being more sensitive, can compensate for it – for a while.

    If it malfs again anytime soon, try soaking the pilot line in solvent – I’ve used isopropyl – and blowing air through it backwards.

    One thing I’ve seen in some propane appliances – don’t know if they’re used in natgas – is an inline gas filter consisting of a slug of compressed brass particles. The idea is to keep gunk away from small gas jet orifices. But the filter itself can eventually fill with gunk. If you can find it and extract it, soaking it in solvent overnight then drying it and reinstalling can revive otherwise mysteriously dead barbecues, camp stoves, propane fridges, etc.

Comments are closed.