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JASPhoto 12-11-2010 11:25 AM

Help with my Gas furnace..Pressure switch and water??
Hi there all, I need your help. I have a 10 yr old Gibson Gas Furnace Model KG6RC100C-16 and yesterday it started having problems. Specs: Itís a gas furnace with internal piezo electric ignition. The April Air thermostat runs as part of our home automation system through a RS-232/485 interface to communicate to the system.
I got a call at work from my wife saying that the furnace wasnít heating the house and when I got home to look at it I noticed it would try cycling through the blowing process and stop within 2-3 mins. Additionally the gas fireplace was having issues firing up, even though I could see the pilot was lit. That finally came one and I think there may have been air in the lines. So back to the furnace. The air filter was dirty so I swapped that out and the blower fired up almost instantly but then it quit again. The LED lights were blinking and the corresponding code said that the pressure switch was stuck to open.
I looked at the whole situation a bit more closely, and noticed that during the 2-3 mins that the unit is running I can hear water running, draining, trickling through the system. Within 30 seconds of hearing the water, the pilot light goes out.
I am trying to decide if itís actually the pressure switch stuck open alone or how the water is playing into the problem. Could it be that the pressure switch closes a valve to prevent water from flowing?

Any and all help would be appreciated. Thanks.

Houston204 12-11-2010 06:33 PM

The factory installed condensate drain on your furnace (shown on page 3) must be cleared.

JASPhoto 12-12-2010 08:07 PM


Originally Posted by Houston204 (Post 549639)

The factory installed condensate drain on your furnace (shown on page 3) must be cleared.

Thank you for your quick response Houston204. I cleared the line as per your suggestion and also installed a new pressure switch (just in case). After firing up the unit, it appeared to be running normally for about 5 minutes then I heard a loud couple of clicks from the new pressure switch (I think) and then the burner went out and the status LED started blinking 2 flashes indicating a "pressure switch stuck open" condition again.

Are there any other possible causes for this condition that come to mind? Any additional advice would be greatly appreciated.

Thank you with best regards,


kenmac 12-12-2010 08:50 PM

take hoses off & make sure water is draining properly from vent motor housing & 2nd heat exchanger. It's stopped up somewhere

hvac kid 12-13-2010 01:43 AM

hey jas. ok what you should do is check the hose going to the pressure switch with an manometer to see if your getting the correct amount of vaccum from your IDM. you might have other promblems like a cracked heat exchanger, too big of a flame, or blower motor. but if your getting correct amount of vaccum the whole time up until it shuts off then you might have a bad control board. if you figure it out then call a pro. good luck

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