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Old 10-20-2010, 09:08 PM   #1
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My Goodman furnace will start the exhaust motor, light up, start the gas flow, ignite, start the blower, then the ignitor tries to light again while everything is running, then the gas shuts off, and the cycle starts over after the blower shuts down. It eventually, after a couple of tries, run and heat. It happens especially in the morning when the setback T/S is set at 62 degrees. It may also happen late at night, but I'm sleeping then. I think it cycles way too often and does not heat enough at that time. What could be causing this? I have a new igniter and flame sensor

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Old 10-20-2010, 10:24 PM   #2
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Do you mean you installed an igniter and sensor and it is still cycling on and off?

BTW 62* is too low a setback. The amount of gas used to recover to even 68* more than eats up what you have saved on the set back.

Is the stat new also?

Need these answers to give the right advice.

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Old 10-22-2010, 07:00 AM   #3
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The stat has been on the machine sine it was new in 1996. I changed the batteries, brightened up the contacts and that changed nothing.
Honeywell Chronotherm III. (I can easily replace it...)

Yes, it's 62 while sleeping. I can set it higher or whatever.Perhaps it's to low, as you suggest??? (What would be a good minimum setting?) We're 1650 sq ft, cape cod.
I changed the filter, brushed the dust off...the ignitor is from Johnstone Supply... the newer version that doesn't break as easily as the original equipment (In one year now) and the flame sensor I installed late last winter.
Your help is MUCH appreciated and will let me sleep at night ( It's5:58 now...) Thanks!

Last edited by Don Cahala; 10-22-2010 at 07:03 AM. Reason: (spelling)
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Old 10-27-2010, 08:28 PM   #4
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I went to Johnstone Supply with the parts book. The guy there suggested, for 19.95, I get the Pressure switch and clean out the Chimney. I cleared a boatload (1/2" ) out of the pipe, then put it back together. I blew through the surgical tube into the fitting, then replaced the pressure switch. Nada. No change except that it hasn't tried tp re-light while the blower is running. That's a plus...
Today I went back, and he said that, since all the other sensors were replaced, the only thing left is the board. I picked one up for 147.00 and will replace it on Saturday. That's it. Nothing left but the wiring harnesses, right? It's still cheaper than getting my ex's old H VAC b/f over here to rake me again for 400 bucks. So this round cost me 147+20 bucks for a grand total of 167.00

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Old 10-27-2010, 09:43 PM   #5
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gee i wonder if I should have told him that model was known for the tube connector orifice on the blower motor rusting/crusting over and not pulling a vacuum to close the pressure switch.

I used to use a very small diameter drill to clear the obstruction....Guess I'm going to hell for that.

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62* is still too low a set back.
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Old 10-27-2010, 09:45 PM   #6
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Originally Posted by hvaclover View Post
I used to use a very small diameter drill to clear the obstruction....Guess I'm going to hell for that.

I hope not . No need for an HVAC guy there
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Old 10-27-2010, 10:24 PM   #7
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I hope not . No need for an HVAC guy there
First thing I'm gonna do when i get to hell is sell Satan a 23 SEER Nordyne.
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Old 11-24-2010, 06:45 PM   #8
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Good points all of them, hvaclover. Especially making a deal with Satan.
This weekend I will try the drill-(I have VERY fine bits in a hand-held chuck I find very handy). I also have an AO Smith water heater that I did that very thing to last spring... it was running continuously and driving me batty. I took the blower out and carefully scraped and cleaned everything I could get my hands on. Short story is, it worked. SO I have every confidence that what you say has great validity- but for those with lower DIY abilities, let it be known we're NOT talking about drilling out the oraface, but merely poking it out to clear out built up debris in that tiny hole.
ALSO- since my GMP-100 was originally down rated to 70,000 BTU, (we had plans to build outward at the time we bought this huge animal) it might be like turning the Titanic around at 62 degrees, and loosing any efficiency that I may have tried to gain with shorter runs and shorter down-times. No wonder my home is above the average in heating during these Wisconsin winters! It's likely better to leave it up so it's not running as often. Next time I'm downsizing to a 45-K 60BTU and I'll likely have a better fit.
Would I benefit from creating 2 zones? (I am very mechanically talented)
Is that expensive to DIY?
OH! BTW- I haven't replaced that board yet. Haven't had the time, but I know I'll FIND time when it breaks down at midnight on Sunday...!
I'll keep you posted. THANKS!

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Last edited by Don Cahala; 11-24-2010 at 06:56 PM. Reason: forgot to add something
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