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  1. #1
    Join Date
    Dec 2009

    Lennox g14 pulse furnace intial ignition problems

    I have a lennox g14 pulse furnace that doesn't ignite on the first time and eventually will lock out ive check gas pressures, cleaned cond lines, replaced board,igniter,flame sense, check combustion blower, everything is going for trial of ignition. wondering if air flapper valve is the problem, dont know when the last time it was replaced, have read forums that say they should be replaced every four years, any suggestions.

  2. #2
    Join Date
    Mar 2009
    central illinois
    get a good tech that knows pulse furnaces
    work to live not live to work.

  3. #3
    The air diaphragm needs to be replaced if it's dirty or worn. You also need to make sure the metal plates that the diaphragm is placed are clean or you can flip the metal plates and just use the clean side. Don't adjust the gas pressure as the pluse valves are set for around 2" wc. The bottom of the drip leg sometimes has a black rubber end cap that can be removed to clean the trap. If it's plastic then you need to flush backwards down the 1/2" drain, the sediment can build up and plug that 1/2 drain. If it can't drain properly then the vent gases will build up causing a flutter when running. If the mufflers are original they can sometimes collapse. Probably the most important thing you can have done, is have the heat exchanger pressure tested. We plug off the collector pipe where it connects to the vent pipe, plug off the air inlet behind the air diaphragm and connect a pressure gauge with port to the gas inlet, once the gas diaphragm and the expansion chamber has been removed. The test is 4psig for 10 min. If ANY pressure is present after 10min then it passes the test. In the last two weeks I have had 3 fail that test. One wouldn't even get to 4psig with the use of an air compressor. Two of them were running and were just having a regular service. Hope this helps.

  4. #4
    Join Date
    Dec 2009
    thank you i replaced the air flapper valve and that took care of the problem.

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