Lenox Furnace - http://www.hvacmechanic.com/ Forums
Original message
| Realtor
 |  "Lenox Furnace"
, posted Thu 17 Nov 18:03  
I have no Lenox Dealer less than an hour away....I have a G24M3-75A-12 Gas Furnace that stopped working. I removed panel and according to Trouble lights it indicates the pressure switch opened 5 times during a single call for heat, or: Blocked Inlet Vent, or Condensate line blocked, or Pressure switch closed prior to activation of combustion air blower. I suspect the pressure switch but am not sure about the condensate line blocked. Any help here? and when I called Dealers in Seattle they will not sell part without a service call (2 hr drive).
Roger
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Replies:
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| moondog
| "Re(1):Lenox Furnace" , posted Fri 18 Nov 07:13
If you have that code, shut off the power to the furnace and turn it back on. With a call for heat, it should try to restart and if it fails it will give you a code which is probably what you are reading. You might remove your intake vent from the furnace if it is not glued in and see if the unit works, and, if so, you may have a blocked vent. If unit runs for a short while you may be able to go out and check the exhaust vent but if it is partially blocked you may not know but the pressure switch will and will shut down the unit. More difficult to determine.
|What is the serial number to that unit?
Lennox had trouble with a circuit board on those units and most Lennox units have a five year parts/labor warranty. The new board is no easy task to install unless you have done a few.
\serial number 58XX------. The XX is the year on Lennox
I would go with the service call and have them check your model and serial number and make sure they have a board upgrade with them just in case. You also have resettable limits on that unit and I believe one is back behind the blower housing. Good idea to know where, so follow the two low voltage wires from the accessable limit or have a tech show you or check the manual.
High efficiency units produce moisture which collects in the secondary heat exchanger and pvc exhaust pipe and must be drained (by gravity) from the unit. Follow the yellow brick road from the furnace to the drain. Some have a vent pipe and you can pour bleach water down and thru the line to keep it clean. Usually a preseason start up procedure. When water backs up into the furnace, the pressure switch picks up on this. Also, dips in the exhaust pvc collect water and cause a partial blockage and pressure switches also pick up on this, usually in low fire with two stage units.
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| fitter597
| "Re(1):Lenox Furnace" , posted Thu 17 Nov 18:54
i would check the furnace condonsate line first, the furnace should drain into a trap then out to a drain line, take it apart and clean it good, check the line and make sure it's clear, make sure the drain or drains from the furnace to the trap are clean and clear too, then put it back together and prime the trap, add water to it, see if that fixes it, if not check your inlet and outlet of your venting pipes, make sure they are clear too, start there before you replace any parts
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| | realtor
| "Re(2):Lenox Furnace" , posted Thu 17 Nov 20:22
Thank you very much, I will do this tomorrow....I do not recall any Condonsate line when I took the panel off to inspect why it quit running, but I will look closer. When I engage the heat setting at the thermostat the furnace blower kicks in and blows but no ignition.
Thanks once again for your help. I will follow up tomorrow with a result from my findings.
Roger
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| | fitter597
| "Re(3):Lenox Furnace" , posted Thu 17 Nov 22:33
If your calling for heat and the fan comes on first it usually means that you have a limit open, like the high limit or a roll out safety, or a pressure switch stuck closed, check the lights again and make sure you are reading the right codes
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