My house is 9 years old. About 5 years ago the Lennox gas furnace began to go into lockout. The problem was diagnosed as a dirty flame sensor. Shortly after, the same problem occurred with the Rheem gas water heater which is near, but not next to the furnace. As a result, the flame sensors on both have to be cleaned or replaced at least twice a year.

The first time I contacted Lennox customer service they advised a reconfiguration of the furnace exhaust/air intake. After that didn't help, I sent Lennox 4 of the replaced flame sensor rods to be analyzed; I never heard back.

One service person talked about fumes from cleaning supplies, paint, even carpeting which may be contributing. Another service person said this flame sensor problem is common and I should expect to have it cleaned at least once a year.

My current plan is to replace both items because at least I'd have a functional warranty. But is this saga familiar to anyone? Thank you for your feedback.


2 Answers 2


Check with your local natural gas utility. That's the company that actually delivers the gas - the same one you call for leaks, but don't call the emergency line for this problem. They may have a pattern of problems, and you would be another point for analysis. Or they may even have a solution.

While different, this reminds me of problems in my area (Maryland) years ago where lots of people got copper b water pipe pinhole leaks. Eventually it was traced to the chemicals in the water and the problem was resolved, though not until after plenty of people (myself included) had to pay to fix their pipes.


I have had issues with gas lines having moisture problems ,and causing failures. I had drip legs in the gas line but had to install longer ones and drain them 2x per year to eliminate the problem. A drip leg is usually close to the appliance just after The shutoff valve. A drip leg is a T with a single dead or capped off pipe pointing down. A drip leg catches liquid and chunks in the gas line that can cause valve and ignition problems. If you don’t have a drip leg you might want to install one after The shutoff valve at the furnace. If you do have one it may need to be drained, to drain turn the gas off, make sure any pilots have gone out and you have fresh air available. Remove the cap from the drip leg and if water flows out you probably found your cause. Make sure when reassembling to use gas rated pipe dope or tape (it is usually yellow). After reassembly and pressurizing make sure to leak test the drip leg with a bubble solution to verify there are no leaks. How long is long enough for a drip leg? I have had homes that only had 4” long legs to the home that had lots of water in the gas needing 12-18” having that much water is unusual but it will cause valve and ignition problems as the water/oil? Contamination causes hot surface igniters to fail. Your problem sounds similar so I would check that as it is something you can do.

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