Rapid cycling gas furnace

A few days back I asked a question about my gas furnace problem. It seems I may have triggered some kind of automatic troll alert or something. How might I rephrase my question to warrant a sincere response. Even if I am an old hack asking a stupid question, I'd still like to know more about the problem if anyone knows. From other questions and responses here I am sure some know and that my question is no more off-the-wall than some of the others. Well, I'm off to the library to see what I can find there. Many good and interesting posts here, so I'll keep reading regardless. -Dan
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Dan;
Go to your local community college book store and see if they have anything on HVACR. You might be surprised. And bring your wallet. The books aren't cheap, but they'll be extremely helpful.
--
Zyp
"Dan Hall" < snipped-for-privacy@dmci.net> wrote in message
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What is the furnace question, you did not ask.
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I paste forward question from original as follows;
After the last response I guess I'm taking my chances on getting an answer to this one- but what the heck.
Forced air 119,00 BTU Nat gas furnace Bryant-BDP-Carrier type Mod # 397HAW036100 Prod # 397HAW036100-ACBA old - as in 1984 installation - new main control board two or three years back.
Problem- Noticed today that it is doing some rapid uneven cycling. Burner on for anything from 1 second to 2 minutes, Off for 30 seconds to 2 minutes until pilot re-ignites, then 20 to 40 seconds to start of next burn. Worse on start up from no run periods and gets somewhat better as it cycles a few times though never evens out - even when thermostat jumped to constant call. Eliminated limit and exhaust purge switches as problem (bypassed with jumper to test) Burners clean with good even blue green inner flame Air flow and filters clean and clear I'm guessing it must be in boards or main valve, but would like to know if I'm missing anything adjustable or minor replace (main board over $100) before I make major decision.
Also noticed occasionally (once every eight or nine starts) takes up to 10 igniter "sparks" for pilot to stay on though normally only takes 1 to 3 "sparks".
The cycling problem is burner only- the exhaust purge fan and the blower continue to run. Thermostat checks okay (bypassed to constant call) "blower delay time" adjustment advanced and retarded slightly with no effect on this problem.
Getting by as is for now (still heating house okay) but uneasy about odd (I think) cycling Any ideas?
Thanking in advance for any comments. BTW- if it matters I worked for heating and plumbing contractor years ago running black pipe gas lines etc.and have installed several new furnaces on my own and done regular maintenance on my own for years. Probably end up getting new soon anyway, but always try to learn as I go. -Dan
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Thanks. I did find some text like references at the library which I am digesting now. Son goes to local CC so I'll ask him to check out texts there as well. Thanks again.- Dan

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