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furnace wont stay running properly lennox g23, this is going to be a challenge,

furnace wont stay running properly lennox g23, this is going to be a challenge,

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  #1  
Old 01-15-12, 01:19 PM
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furnace wont stay running properly lennox g23, this is going to be a challenge,

hi and hello, i have just bought a home and i think furnace worked fine, but now problem is it will always ignite and run and then shut off, blower keeps going and it will ignite and repeat cycle, it will eventually get to temp after hours of doing this, it should run till it hits desired thermostat temp but it is not, it is like a safety switch is shutting it down, i had to put a new bcc-3 board in yesterday, one of the relays was burnt on it litterally,, took filter out, opened all registers, cleaned everything, i need help, ideas of what to check, i had a half ass repair man out ,he did know good but took my money, i ordered the bcc board and chose that as my first choice and it did the trick from what i had , inducter motor runs, main blower runs, it ignites always just wont run consistent to desired set temp , need some help here, when temp is reached as in now it does shut down completely , any tips would be helpful thanks , also when it does fire and run it only goes full bore for a few minutes, does a cool down i guess as blowers still run , then fires and burns again, it is prob a 1997 yr model it doesnt have code lights to read , it is all mechanical besides for bcc-3 board
 
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  #2  
Old 01-15-12, 02:50 PM
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It sounds like you are shutting down on high temp limit. You have already replaced the filter and verified ALL registers are open then you need to verify the evap coil of the air conditioning is clean. This is typically located right above the furnace.
 
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Old 01-16-12, 01:41 PM
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hi

i jumped out thermostat same condition, i went on roof cap and all looks good and clear, i raised a-coil up about 1.5 inches above furnace, air could blast out of there no problem ,all registers are open and took filter out ,, same problem
 
  #4  
Old 01-18-12, 08:23 AM
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I had the same problem and it ended up where I bought a new thermostat (just a regular, non fancy, honeywell). It cleared up the problem.
 
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Old 01-18-12, 03:22 PM
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Does it have a pressure switch and related tubing? Might have intermittent clog in these?
 
  #6  
Old 01-18-12, 03:52 PM
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Very likely the limit switch is opening because the furnace is overheating.

I'd start by measuring the voltage at the limit switch to verify that the limit switch is open and is shutting off the burners. The best way to do that is to use a multimeter to verify that the 24 VAC shuts off at the limit switch when the burners shut off.


And exposing the AC coil from the bottom and observing airflow coming out of it does no good. The problem is that the AC coil may be plugged with debris and preventing air from freely passing through the coil. If it's plugged you are naturally going to get a strong air flow coming out the gap you created.

You need to lift up the AC coil and inspect it for debris that may be plugging it.
 
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