American Standard gas furnace won't start

Old 11-03-04, 12:06 PM
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American Standard gas furnace won't start

I have an Amer Standard 90%+ gas furnace which intermittently won't start when it calls for heat. The blower fan comes on for a minute and then shuts off for a couple of minutes, etc. The circuit board flashes 3 times signifying a pressure switch problem. I called the installer, who doesn't repair furnaces, and he said to turn the furnace off, remove the air hose from the front of the pressure switch, blow in and out 2 or 3 times , reconnect the hose and turn on the furnace switch. This fixes the problem for a few days but then I have to go thru the same routine again, never when the furnace is hot only when it sits cold for a few hours. Lately I've had to do this routine every morning.

My questions are... How can I be sure that the problem is the pressure switch ( they cost $200 ) and not something else causing the switch to malfunction? Is there something else which may be causing this problem?

Thanks for your help.
Old 11-03-04, 05:50 PM
rav12's Avatar
Join Date: Oct 2003
Location: California
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How about bypassing the switch every night after turning off and seeing if it will fire up in the morning. If this works then the chances of it being a faulty pressure switch are much higher.

Once you get it going in the morning I would suggest removing the bypass for the day for safety reasons
Old 11-04-04, 10:06 AM
mattison's Avatar
Join Date: Mar 2003
Location: Cinti, OH
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You should check it out closer. The tube is probably getting blocked by something in the duct or condensate is somehow getting in there.

These switches do go bad sometimes.

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