Lennox Pulse 1992 - Stumbles on startup - http://www.hvacmechanic.com/ Forums
Original message
| jjm9354
 |  "Lennox Pulse 1992 - Stumbles on startup"
, posted Sat 10 May 09:56  
Hi,
My Pulse is not one of the ones that had all the problems (I think that was 1991 and before). It's been great for 16 years but lately seems to stumble on startup. When it calls for heat, instead of immediately starting it occasionally misses, and ignites after about 5 seconds. It sounds something like a 1965 Pontiac Catalina that keeps running after you turned the ignition off (dieseling). I have it serviced every year.
Thanks
Jim
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Replies:
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| yuri
| "Re(1):Lennox Pulse 1992 - Stumbles on startup" , posted Sat 10 May 13:12
Great furnace when they work properly. Huge pain the the a** when they don't. Have worked on them forever. You may need a new flame sensor or air flapper or gas flapper and need a highly experienced Lennox guy to fix it. Very specialized furnace. Some of them had a blockage problem where the gas enters the heat exchanger which can cause your problem.
Good Luck
Yuri
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| TnNATE1412
| "Re(1):Lennox Pulse 1992 - Stumbles on startup" , posted Sat 10 May 13:11
You could very well have a larger crack in the heat exchanger. By the way, Pulse furnaces have a leak rate no matter what. The sensor could be bad, or unless you have had the the control changed out to the new blue ignition control, your ignition control could be bad. The gas valve could also be going bad and not regulating the pressure properly.
And for the record, for non-Lennox techs, Pulse furnaces only fire at 2" w.c. on natural gas and 10" w.c. LP pressure. They will stumble at higher or lower pressures.
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| | TKG26
| "Re(2):Lennox Pulse 1992 - Stumbles on startup" , posted Sat 10 May 15:02
-Air flapper should be replaced every 4 years
-Heat exchanger should be pressure tested every 4 years
(that is as per Lennox)
Chances are you need to have the airflapper replaced. Get a lennox dealer in or a tech that knows the pulse furnace.
There are many things that could cause ruff starts:
-air flapper
-gas flapper (erratic manifold pressure)
-colapsing mufflers(you probably have the white ones but if they are grey its a high proability of being a problem)
-the gas outlet into the combustion chamber could be rusting over, so rare i have yet to see it
-gas pressure out of wack have adjusted back to normal there is typically a 1.5" to 2.5" allowable manifold pressure
-dirty flame sensor and ignitor, better to replace after 16 years.
-most 92+ models have the blue johnson controls but they have been knonw to fail too
By the way locally Lennox has been jacking the price up and "kitting" up parts like the gas flapper and plugs and calling them tune up kits but raping for 900-1500$ for the kits, in most case your only after one or 2 parts and the rest of them are not needed or at least not worht what they are chargin
Some think this is becuase they are trying to push customers to replace instead of repair those units as they have stopped producing heat exchangers and these units all have 20-lifetime warranty. Last i heard they will replace the furnace for a flat install rate but i think this is there way to force a sale instead of warranty repair when the heat exchnager fails....
Could be purely BS but this is the info i got for the local lennox wholesaler
SIGNATURE "Always have a licensed HVAC technician perform repairs on your equipments. HVAC is not a do-it-your-self home project."
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| | yuri
| "Re(3):Lennox Pulse 1992 - Stumbles on startup" , posted Sat 10 May 19:29
Welcome back, long time no hear.
They will now credit the Lennox dealer $500 towards a G51 if the heat ex fails the press test. Must be original owner with proof. 2nd owner gets 20 yrs. Lennox dealer gives buyer $500 off the sale of a G51 or G61MPV or G71MPP. I do lots of press tests and am a Lennox tech (Service Experts).
Pulses are a pain to work on because of the multiple problems and intermittent problems they can have. Quite expensive to repair and very few guys know them that well.
Yuri
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| | TKG26
| "Re(4):Lennox Pulse 1992 - Stumbles on startup" , posted Sat 10 May 22:52
ya its been a while.
The pulse as a technician you either love them or hate them. I did so much work on them during the recall years that im pretty comfortable around them... You have to trust you manomator and you instincts :)
SIGNATURE "Always have a licensed HVAC technician perform repairs on your equipments. HVAC is not a do-it-your-self home project."
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| | yuri
| "Re(5):Lennox Pulse 1992 - Stumbles on startup" , posted Sun 11 May 10:24
Exactly. Have one in Mom's house that is 25 yrs old. Hate workin on them after all the recirculation/venting problems.
Yuri
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