Lennox pulse ignition failure

This one is about an ignition failure on the Lennox pulse gas furnace that can related to a cracked heat exchanger.
This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits.

12 Replies to “Lennox pulse ignition failure”

  1. My pulse sometimes just won’t kick on right now the flame detec is off and it’s not ignited at all. Tried resetting things and this has happened before but it’s definitely frustrating, but I know it needs replacing as it’s 20 ish years old.

  2. I have a Pulse 21furnace that seems to run fine but after a few hours or days it starts blowing cool air requiring me to turn it off and reset the control module. The air flapper has been cleaned (a new one is on order) and the control module replaced this past Oct. Any ideas? Thanks!

  3. My lennox pulse G14 sputters as it gets warmer and I think it is going to die but it continues to reach temperature. It runs smooth then reaches a certain point boggs down for a couple seconds then smooths out for about 10 seconds. It cycles like this and reaches temperature. If I turn up the temperature quickly it trips out the ignition sometimes.

  4. Lennox Pluse (10/1987) G1404/5-100-6 still chuging along. Replace flapper about every 4 years. Had to change Fan Limit switch – HOWEVER generic limit switch cause Blower to short cycle. So had to add Delay -Off-Relay set to 4 minutes (that feature was built into original fan limit switch).

  5. I have a lennox pulse it runs perfect but the lennox guy told me he doesnt recommend i run it its too old . Im guessing hes just trying to sell me a new furnace. Cant see a reason to stop using a perfectly fine furnace. Im for maybe replacing it but i feel pressured to do it now when i see no reason for the rush it works great

  6. My Pulse will not always respond to the thermostat's demand for heat but it will start right up when I switch the power switch off and then on again. Then it might run for several days with not problem. Does this sound like a thermostat issue or a furnace issue?

  7. the best thing to Do is get rid of that piece of shit! I have replaced a lot of those. Lol…

  8. Hi grayfurnaceman, a buddy of mine gave me his old Pulse for use in my garage. I'm halfway thru the installation. I want to omit the mufflers from the inlet and exhaust as again, it's in my garage, no need for quiet. Would omitting the mufflers in any way effect the performance or will it effect the omission of CO2 gas?
    thanks in advance

  9. I have a question for you grayfurnaceman. I have a Lennox Pulse G14 and i was wondering what a particular part is called. Its the metal cage that surrounds the air flapper valve assembly. Im trying to locate a replacement

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