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bdarnay · Jan 30, 2007, 01:12 PM

I have a Goodman 93% efficient furnace that short cycles the gas burners. It cycles the vent on, starts the igniter, fires the burners and kicks on the blower but the burners only stay on for a short time ( less than 30 seconds). The led on the circuit board gives me 3 flashes indicating " pressure switch failure to close". The unit is venting properly and the hose from the venter to the pressure switch is not blocked. Any idea how I check the pressure switch or is there something else I need to check? I should also say that all this happens after the unit has been powered off and powered back on @ the circuit breaker and will run for several hours exactly as it should without said problem. Thanks

NorthernHeat · Jan 30, 2007, 04:43 PM

Is there a pipe for the combustion air ran outside? How old is it? Could there be water in the exhaust pipe or not enough fall back to the furnace? What BTU, sixe of pipe, length of pipe and how many elbows. I run into this all the time, installers push the envelope on the venting requirements.

bdarnay · Jan 30, 2007, 05:31 PM

16' of 2" PVC pipe with 2 elbows, the first elbow is at the lowest point and has the drain spigot running to the condensate pump that is working. The PVC runs to the outside of the house, is apporximately 10 years old, falls 3 inches back to the furnace in 12', not clogged and is definitely exhausting to outside of house (easy to see during the winter).

hvac1000 · Jan 30, 2007, 05:39 PM

Check with a goodman supplier or the factory. I believe there were some problems with the pressure switch settings that would effect units as they get older. The fan does not put out enough for the switch to always activate
OR just replace the switch.

NorthernHeat · Jan 30, 2007, 06:17 PM

Is it on LP, is there soot in the vent pipe, (black)? And yes! Like hvac1000 said, it is not hard to believe a 10 year old pressure switch is bad.

bdarnay · Jan 30, 2007, 07:18 PM

Natural gas and there is no soot in the vent pipe.

bdarnay · Jan 31, 2007, 08:23 AM

One other thing I noticed today when I turned off the system to reset I could hear a sizzling sound coming from the secondary heat exchange. Could this be part of my problem?

hvac1000 · Jan 31, 2007, 09:58 AM

Is the drain open for the condensate water?

bdarnay · Jan 31, 2007, 10:50 AM

Drain is open and water is flowing from pump to drain

NorthernHeat · Jan 31, 2007, 04:25 PM

Originally Posted by bdarnay

Drain is open and water is flowing from pump to drain

Ok from pump to drain... But it could be running slow from furnace to pump, the sizzeling sound makes me think there is too much water in the furnace.