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Chippewa 02-09-2012 09:28 AM

Goodman pressure switch
I replaced the heat exchanger on a goodman 90% last night. When I went to start the furnace the pressure switch that sees the pressure from the cover of the condensate pan was not making. I bypassed it and ran it for about fifteen minutes. At that point the pressure switch was making so I placed the furnace back into normal operation. About two hours later the homeowner called back with the same problem. I am sure the pressure switch is good, but I did not have a negative pressure guage on me at the time so I am not sure what the pressure actually was.

Doc Holliday 02-09-2012 10:58 AM

Clear the flue pipe and/or the ports where the pressure switch TUBE connects to on the draft inducer motor and the pressure switch as they could have crud in them. Stick an unfolded paper clip into the ports where the tube connects to clear them out.

The drain line could have condensation/crud in it as well which would not allow the pressure switch to close.

Did you seal the heat exchanger properly?

Chippewa 02-09-2012 12:52 PM

The heat exchanger came as a whole unit, meaning the primary, secondary, front cover, and drain pan were all one piece. The tube in question feeds off of the secondary heat exchanger cover and should pull a -.75. There is an additional switch that also pulls a -.75 which pulls directly off of the wheel housing. I switched the switches and the problem did not move so I am sure it isn't the switch. I did try and clear out both the tube and the tap. Since the unit came as one piece I am really not sure what could not have been sealed properly. I do know it is pulling a vacuum but I am not sure as to what specific number it could be. Voltage flows (or doesn't flow right now) through the switch directly into the gas valve so the code is a failure to fire. I really didn't check the condensate line well. With everything being new I don't think it is build up. It never fired from the start either so I don't think it is back up. I will be going back tonight with a gauge so I can see what vacuum it is pulling, but I am at a lose as to my next step. I feel as though I am missing something since the pressure switch was not a problem before I took the old exchanger out.

flashheatingand 02-09-2012 01:44 PM

Take a look at the solder joints on the back of the control board. Goodman has had problems with cracking solder joints on their boards.

Chippewa 02-09-2012 08:49 PM

I am getting 24 volts at the switch though. It just isn't closing.

Dr Heat 02-09-2012 11:00 PM

I had A Heil that had a pressure switch issue after a heat exchanger. The end result was grease from the manufacturing process had plugged the secondary. Had to pull the secondary and poor hot hot water on it for a long time to get the grease to melt out. The whole process took several trips and many many hours.

Chippewa 02-10-2012 08:20 AM

That sounds like the problem I may be dealing with. Thanks, I will give that a try.

flashheatingand 02-10-2012 09:46 AM

If that is the case, I would want a new furnace. That shouldn't be a burden that the h/o or the repair guy should hold. If you can prove the heat exchanger was cracked and the replacement exchanger was faulty as well, the burden lies with Goodman, or whomever.

That being said, I would make sure the nipple
port on the h/e is is clear. It sounds like you have quite the pickle and would love to hear the outcome.

greenleafmech 02-19-2012 04:25 AM

Did you get this heat exchanger under warranty? Did you also check the warranty disclosing on this particular furnace?

Chippewa 02-19-2012 08:54 AM

I did get the heat exchanger under warranty. When I went back with a magnehelic the pressure was fine. I decided to let it run and just see what happened. It has been over a week and it is still working fine.

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