Keeprite Furnace *cycling*

My 12 year old Keeprite furnace is heating the place OK but its cycling without firing up intermittently. Sorry for the non-technical description but here goes: when I listen to it fire up normally, I hear a click followed by the flue fan (draft inducer) motor coming on and then the gas ignition and heat. But recently, it has started doing all of these without the gas ignition and heat. It sounds like its trying to fire up but failing for soem reason. Anyone got any suggestions before I call in a tech.
Thanks.
Jimbo
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I had the same happen with a Sears induced draft gas furnace. The flue blower runs and runs and runs but no gas and no heat.
The problem is the safety switch that detects the flue draft pressure is stuck OFF and so prevents the gas valve from opening.
This device has two hoses attached to it that go to the flue blower and two wires. You may be able to TEMPORARILY by-pass it to have heat now. Switch the furnace power OFF, disconnect the wires from the safety switch and jump them.
Order a replacement - it's there for a good reason.
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On Mon, 12 Dec 2005 17:42:02 -0800, "T.G. Lambach"

Bypass a draft pressure switch? TG, you are a fuckin idiot. Yeah it might get him heat and it might also get him dead. The pressure switch could be doing its job by letting you know that the furnace has a big hole in the heat exchanger. Would you like me to tell you about the one I found today with a hole in the secondary big enough to put my fist in? It was running when I got there. Some idiot told him how to jump the pressure switchWas it you? 1000 ppm in the flue. Was it you? Bubba
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T.G. Lambach wrote:

Because a safety is there for a good reason it's best not to by-pass it. Never ever bypass a safety unless you're a qualified tech troubleshooting the system. Even so a volt/ohmeter is the preferable test for open limits and safeties when that option is available. Nobody under any circumstance should ever leave a furnace running with safeties jumped.
BTW, it's most likely not an open safety or limit given the OP's description of his observations. It is likely an ignition failure problem, but then we can't see it from here, so it could be that the gas has been shut off, the gas valve is shorted or open, or any of a hundred other things.
hvacrmedic
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You can see that from where you sit? Man, I have a job for you....seriously...couple of hundred an hour, if you are that good...just pack up, and MAKE SURE YOU BRING YOUR CRYSTAL BALL WITH YOU!!!

Yea,....so is proper troublshooting advice, not that any was given.
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T.G. Lambach wrote:

Because a safety is there for a good reason it's best not to by-pass it. Never ever bypass a safety unless you're a qualified tech troubleshooting the system. Even so a volt/ohmeter is the preferable test for open limits and safeties when that option is available. Nobody under any circumstance should ever leave a furnace running with safeties jumped.
BTW, it's most likely not an open safety or limit given the OP's description of his observations. It is likely an ignition failure problem, but then we can't see it from here, so it could be that the gas has been shut off, the gas valve is shorted or open, or any of a hundred other things.
hvacrmedic
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Yes, Get a tech before you get suggestions. We cant see it from here. Bubba
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Boys, please. Thanks for the suggestions but let me be clear, I'm not looking to replace a tech by posting on here. My hope was that someone could simply suggest how big an issue this is before I call in the tech. TG's suggestion of checking the safety switch is fine. In fact he did very clearly state *TEMPORARILY* in his post. As for the idea to get a tech before suggestions, I've been burned that way before. Nowadays I like to have some clue before handing over that blank cheque/check :) If anyone can recommend an honest tech in Toronto, I'd be happy to give him/her a call.
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Jimbo wrote:

We know what he said, apparently you don't yet.
hvacrmedic
As for the idea

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So, RP, is there any additional information I can offer or get that might help someone help me analyse the problem. I'm not trying to put anyone out of a job - just trying to gain a little knowledge.
Thanks in anticipation.
Jim
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Jimbo wrote:

If you had read my previous post you would have found plenty to work with without me actually telling you point blank what the problem is. With a few more fill in the blanks I could probably do just that with a comfortable margin of error. Hot surface ignitor or spark ignition? Gas bill paid up? Smell gas during this sequence?
hvacrmedic
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On Friday evening, I shut everything off, and spent 20/30 minutes cleaning every surface I could easily access. Also, I checked all connectors and contacts. Afterwards, I vacuumed all debris and switched everything back on. For now, everything seems to be working correctly.
Thank you all for your help and guidance.
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