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HardcoreNinja69 02-01-2011 05:49 PM

Lennox Furnace in Watchguard mode
My Lennox G40UH-36A-070-03 furnace if giving me trouble recently. Over the past two weeks, it has ended up in Watchguard mode:
A: Burners failed to ignite
B: Limit open more than 3 minutes
C: Lost flame sense 5 times in one heating cycle
D: Pressure switch opened 5 times in one heating cycle
This just circulates the cold air through the house. I have woke up a couple morning with the temp down quite low. I live in MI so this is a big deal with the weather we have had/are having. I have replaced the air filter, taken the flame sensor out and cleaned it with sandpaper and reinstalled it. The igniter gets red so I don't believe thats the problem. At times it runs fine. When it fails to light, I occasionally get flame on one burner(not even always the same burner) and then it goes out within a couple seconds. Most often it doesn't actually get flame. I can smell gas if I check it after it cycles so I don't believe thats the problem. In a possibly related problem with the pilot on my water heater going out. I changed the thermocouple and it still seems to have the same issue. Is it possible for it to be a ventilation issue? The exhaust from each merge together and exit my house from the same vent. I have lived here for about a year and a half. The furnace was installed in 2002. I have tried reading up on other threads to solve the issue prior to posting. I appreciate any and all help I can get to rectify my situation.


yuri 02-01-2011 05:54 PM

Probably your gas meter and/or it's regulator are failing and losing pressure intermittently. Seeing that the problem happens with the water heater also it sounds like a supply problem. Call your gas supplier and tell them the symptoms. Hard to diagnose that problem but I have had it happen several times. Check the meter and regulator outside and make sure they are not buried in snow or ice, there is a small screen on the vent of the regulator, make sure it is not blocked.

HardcoreNinja69 02-02-2011 10:09 AM

Thanks for your suggestion yuri. I called the gas company and they came out and checked the line pressure. It was variable so he swapped out the meter and now is constant. Hopefully I won't have more issues.

yuri 02-02-2011 01:40 PM

Glad they found it as those intermittent problems can take several visits and complaining to them to get resolved.

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