Sometimes it gives heat, Sometimes it won't

[TheFixer300]

i am having problems again this year with my pulse21 about 3 years ago, had a lennox tec out, and after swapping several things, it was determined my air flapper was bad, and he replaced it. worked fine for about 3 years, and again comes the cold weather, and the furnace won't kick on. i get into the air flapper area. (only takes about 3 or 4 minutes to get all the screws/bolts out and get the part out. it wasn't that bad, but i cleaned it, and put it back together, and back in place. kicked on the furnace, and it fired right up. worked for maybe 4 cycles, and quit again. i started looking for obstructions in the air in/out and vacume lines. nothing wrong. when you reset the power to the main unit, you can hear the air chamber blower kick on, and the sound of a pulse heard, but when you hear the click for the spark to come on, nothing happens. after several tries, the main module's light blinks off/on. so a reset is necessary. i stumbled on getting the furnace to work, but seems to only work for maybe 2 days. then if i do this again, another 2 days. can anyone shed some light on what may be occurring.  i take off the air flapper, and clean it. (not really dirty) but before i screw it back in place. i put a small vacume cleaner up to the (not sure what this is called  the unit that the air flapper assembly fit's on) and press it as tight as i can to the opening, (a small vacume, and the hose end is just the right size) that leads to the inside. nothing can be heard coming into the hose. but after i do this, the furnace runs with no problems for like i said a couple of days. what in god's name, can the vacume cleaner procedure have to do in getting it to run. what is inside the unit being vacumed out. ??

anyone have any ideas on what i can replace in there or what is happening. 

  thanks  Jim

[kdog]

the way you describe the problem,souns as though you may have a problem with the burner ignitor as it likely has a build up of carbon so it does not recognize the burner is lit and sends the control into a lockout mode.

[Crouching Tiger]

[user=15682]TheFixer300[/user] wrote:

you can hear the air chamber blower kick on, and the sound of a pulse heard, but when you hear the click for the spark to come on, nothing happens.

When you hear the sound of the first 'pulse' this is the only time there is a spark, after that combustion is self-sustaining.  How soon after ignition does the 'pulse' sound stop? - before of after the main blower comes on.  My own Pulse furnace had a plastic 90' fitting cracked where the differential pressure switch hose connects to the exhaust tubing.  Make sure you are absolutley sure there are no restrictions or cracks in the tubing or hoses - this includes the condensate drain tubing.  Lennox also prefers you to change the air flapper every four years regardless of condition, although my unit is 10 years old and I have never done it.  Also check for any possible changes to where the intake/exhaust tubing terminates outside - exhaust could be recirculating with intake air stopping combustion. 

[jahjahbinks]

i have had to deal with lennox on this problem /// the bottom line was to replace it

the flapps wear to fast

 

INFO COMES DIRECT FROM LENNOX , ALSO UNABLE TO REDUCE NOISE

PRODUCT // DEFECTIVE