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Old 02-21-2012, 12:59 PM   #16
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Lennox G20E Gas Furnace Down; What next?


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If you are getting 24-28 volts at the input to the module then it should produce a spark unless the spark wire is shorted to ground and that can happen as it dries up and goes thru sharp metal. Take the spark wire off and hook an alligator clip and wire to the terminal and hold it 1/2 inch away from the metal box and wear gloves and see if it sparks. 99% sure it is the module and definitely go with the Honeywell 30w33 from Cozyparts.com as it is the Lennox part and has great install info. also has new built in diagnostic features which is better than any generic unit.
Aw heck, Yuri, i always wet my finger and touch the the spark generator
terminal.....what's ten thousand volts with no amperage...just wakes you up is all.

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Old 02-21-2012, 03:26 PM   #17
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Lennox G20E Gas Furnace Down; What next?


Quote:
Originally Posted by yuri View Post
If you are getting 24-28 volts at the input to the module then it should produce a spark unless the spark wire is shorted to ground and that can happen as it dries up and goes thru sharp metal. Take the spark wire off and hook an alligator clip and wire to the terminal and hold it 1/2 inch away from the metal box and wear gloves and see if it sparks. 99% sure it is the module and definitely go with the Honeywell 30w33 from Cozyparts.com as it is the Lennox part and has great install info. also has new built in diagnostic features which is better than any generic unit.
Thanks for the tip. Since I am not hearing any clicking, I suspect the ignition control module is not sending any voltage to the ignitor. I think I cannot debug any further till I get a working ignition control module. 30W33 (not sure how this is different from 33W3301) seems to be a consensus recommendation.

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Old 02-21-2012, 03:54 PM   #18
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Lennox G20E Gas Furnace Down; What next?


<< deleted this>> added this information to earlier posting.

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Old 02-21-2012, 04:48 PM   #19
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Lennox G20E Gas Furnace Down; What next?


30w33 is the same as 30w3301 Lennox uses 4 digits after the letter but most people drop the last 2 for convenience.
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Old 02-24-2012, 05:21 PM   #20
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The furnace is up again after the new Lennox 30W33 ignition control module. Thanks a lot for your help in the diagnosis and the eventual fix.
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Old 02-24-2012, 05:25 PM   #21
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Yer Welcome.
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Old 02-27-2012, 12:15 PM   #22
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Lennox G20E Gas Furnace Down; What next?


Now that the panic phase is over, I am wondering if I should have gotten Honeywell S8610U3009 ignition control module instead. Not sure of the changes but S8610U3009 has replaced S8670K3000 part that the Lennox 30W3301 kit came with. Not doubting the excellent advice I got but I am just curious.
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Old 02-27-2012, 12:37 PM   #23
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Lennox G20E Gas Furnace Down; What next?


it may look the same but they are not the same control. the 30w33 control has a prepurge timer to allow the damper door to open and purge the heat exchanger. the universal one does not and technically voids the UL and CGA certification of the furnace.
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Old 02-27-2012, 12:57 PM   #24
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Lennox G20E Gas Furnace Down; What next?


PP 15 of the S8610U Installation Guide claims that S870U3009 has DIP switches (SW1 and SW2) that can be adjusted to make it behave like S8670K3000. Again, not doubting the excellent advice and notwithstanding the fact my limited experience/knowledge may be leading me astray, I just wanted to share this in case it may benefit someone who may try to attempt a similar repair in future. If both parts are indeed functionally equivalent, a braver person probably can go with S8610U in case it is cheaper than S8670K.
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Old 02-27-2012, 02:14 PM   #25
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As long as they get the NEWEST version of it and not one that does not have that feature. The 30w33 comes with the proper wiring instructions and crossover chart for the wiring and mounting bracket and adaptors etc which the universal one will not. Most Pros could figure it out but I would not recommend a DIYer try. Makes no difference to me what a DIYer does but safety comes first and I have seen too many botched wiring jobs and dangerous situations to recommend DIYers who are not experienced use uiniversal controls.
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Old 03-07-2012, 11:28 AM   #26
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Lennox G20E Gas Furnace Down; What next?


After working fine for 8 days, the furnace went down again. This time, the ignition control module cannot start the blower and shuts down the furnace soon after to avoid overheating. After resetting the ignition control module, I can force the blower on via the thermostat. Not sure where I should start my debugging. Any suggestion?
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Old 03-07-2012, 05:27 PM   #27
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Lennox G20E Gas Furnace Down; What next?


Start at the blower control board,not the ignition module.
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Old 03-07-2012, 05:32 PM   #28
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Lennox G20E Gas Furnace Down; What next?


Thanks for the suggestion. Not sure of the root cause yet. I wonder if something more basic first fried the ignition control module and now the blower control circuit board. It would be wonderful if I can find a root cause this time so the fix will be permanent.
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Old 03-20-2012, 10:34 AM   #29
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Yesterday I tried to do some debugging on this. I shorted the fan limit switch but it still didn't start the blower as expected. As mentioned before, the blower can be forced ON from the thermostat just fine. I also tried the AC and as expected, the blower came on just fine in this case as well. I would conclude that both ThermoStat ON and AC bypass the BCC (or more precisely, the faulty part/s on the BCC). On a cursory look, the BCC looks undamaged and is getting the 24v to it. I will look this some more tonight. Any pointers? I am a little nervous just replacing part after part without understanding some probable single root cause for both ICM and BCC failures.
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Old 03-20-2012, 12:37 PM   #30
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Lennox G20E Gas Furnace Down; What next?


What's the BBC connection you refer to?
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