Lennox furnace problem: ballpark cost to fix?

I do already have a service call scheduled for Thursday morning, but I wouldn't mind having a rough idea how much the problem might cost to fix.
It's an 8-yr-old Lennox G32 that we turned on (that is, we switched the thermostat from Cool to Heat) a couple of days ago. We hear the blower start up, but it stops a few minutes later without the set temperature having been reached.
The LED indicators show that the burner has not ignited, and there is a strange noise when the blower is running -- not exactly a rattle, but it sounds as though something may be rubbing/scraping against something else.
I know that the HVAC company we've called advertises furnace inspections for $69, but I don't know how much time that covers, and obviously it wouldn't cover any needed parts.
Any intelligent estimates?
Perce
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Percival P. Cassidy wrote:

    Can't give you an estimate, but I have a question and suggestion. First most furnaces go into a lock down mode if they fail to start properly after something like three tries. If your furnace is in lock down mode, you should turn off the power to the furnace for about five minutes and try it again. NOT the thermostat, but the power to the furnace. It might just start.
    You say you hear a noise when the blower is running. By blower you mean the inducer fan for the exhaust?? Not the blower that circulates heated and cooled air in your house??
    If the inducer fan is not functioning properly, that could well be the reason your furnace will not light. Determine where the noise is coming from.
    Finally, nothing is cheap to fix if a service man visits your home. At least not that I am aware of. List more info.
    
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On 10/05/10 03:05 pm, Ken wrote:

had tried that already.

Yes, the inducer fan. I did not know that term before. In the meantime I had googled "Lennox G32" and found one report of water in the inducer fan housing. That had been my first impression of the sound (but I discounted it and didn't mention it because I couldn't see how water could have got in there), so I removed the rubber "flue transition" and found a lot of water accumulated there and in the fan assembly. Any simple way to get rid of the water? And figure out how it got there? And even be able to solve the problem without the service call?
Perce
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Percival P. Cassidy wrote:

    Well it seems you have found your problem. I would assume the water is coming in from the exhaust flue via the stack going through your roof. It should have a cover on it that prevents water entering the flue. You need to correct this situation.
    As for removing the water, it really depends upon how the inducer fan is mounted. Generally loosening the ducting should provide a way. I might suggest using a syringe to remove water that has settled in a low area. A turkey baster works well for this if you put a rubber hose over the end of it.
    So your immediate problem is to remove the water, and then you need to look at the flue to see if the cover where it goes through the roof is preventing water from entering. You might very well have avoided a expensive service call if the water has not damaged the inducer. Let us know how you make out.
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On 10/05/10 05:05 pm, Ken wrote:

Not water (e.g., rain) coming in but condensate not getting out due to a blockage in the condensate drainage system (common on this model, it seems). (Our inlet and exhaust pipes are horizontal, anyway, and come out through the end wall of the house.) I disconnected the drain tube and an elbow that is particularly prone to blockage and flushed them out. I then removed the inducer fan (just four screws), tipped out the water, and put everything together again.
Right now everything is working fine.
Thanks for your suggestions,
Perce
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Percival P. Cassidy wrote:

    Good to hear you solved your problem. Since each maker of furnaces has a different design for their product, it is difficult to envision just how they have everything connected. For what it is worth, the thermostat first calls for heat. Next the inducer starts and if the switch meant to detect a pressure change in the flue senses the inducer running, the igniter is activated and then the gas is opened. There are other safety checks, but that is roughly the sequence.
    You just saved yourself a couple hundred dollars, at least.
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I'm sure the techs on alt.hvac would be screaming now, that a home owner fixed his own furnace. I'm happy for you. And sad for a service company that lost a call.
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Christopher A. Young
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A relatively common fix on PVC stacks is a "U" bend causing the exhaust to vent DOWN and making it virtually impossible for water to get in.
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Look for a drain (rubber tube) from the inducer to where the other water is draining. Could be clogged.
90% furnaces condense the water out of the flue gasses, so they (90 percenter furnaces) need a drain.
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Unlike A/C the furnace has to have a clear exhaust and a vacuum switch prevents ignition. I'm betting you have a clogged PVC vent (leaves or rodent nest). The blower is the same...so maybe the crap is scraping the exhaust gas fan.
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On 10/05/10 03:06 pm, Bob Villa wrote:

See my response to Ken: water, not leaves or rodent nest.
Perce
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A minute late...good going Percy!
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