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Old 09-19-2012, 01:20 AM   #1
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Rpg heat exchanger blowing cold air


My furnace just started blowing cold air. The red light flashes three time indicating pressure switch stuck open. I havr read a couple other post but could not find the answer. The furnace is vented through pvc. Where and what does this switch look like? Is there a way to know if thos is my problem?

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Old 09-19-2012, 07:18 AM   #2
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Rpg heat exchanger blowing cold air


it is hardly ever the switch that is the culprit. Make sure the small fan motor located near the burners operates with a call for heat.

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Old 09-19-2012, 07:33 AM   #3
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Rpg heat exchanger blowing cold air


4" round like this with 2 thin wires gong to it,the stat cal the furnace as said the ID runs the switch senses air into the heat exchanger...and the ignition goes..then the main burner....set the stat all the way up in heat..sit at the furnace using the service switch to cycle restarts.note the cycle after the ID starts....if for any reason that switch bounces during a heating cycle the burner will restart,as your is it might be stuck open ..check tubes blow thru them or as simple as tapping the silver pressure switch with the handle of a screw driver....to simulate a start toggle ON...when the ID starts put the 2 wires togeater the cycle should follow.....2 wires have to stay together...seperate them and you'll get your light on the board http://www.bestbuyheatingandaircondi...ode=PRS06NB065
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Old 09-19-2012, 08:42 AM   #4
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Rpg heat exchanger blowing cold air


make sure the pvc pipes are not restricted ...inlet and exhaust.....
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Old 09-19-2012, 12:01 PM   #5
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Rpg heat exchanger blowing cold air


The pvc lines seem good and i blew through the pressure switch lines. Still no heat and three red flashes. When it does heat i should be able to see a flame through the little windie right?
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Old 09-19-2012, 02:19 PM   #6
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Rpg heat exchanger blowing cold air


did you reset the 115V service toggle on the furnace then do a restart.did you remove the tubes or disconnect them and blow into them...if power was up the circuit board would pick up the fault.with the power off blow into the input tube lightly...to the pressure switch and do you hear a clicking ..if not the switch is rusted shut...that switch has to be open before the ID starts then stay closed during heating...any bounce is a red light 3 locks the heat.....go for that power reset shut the stat off with heat do reset then call the stat back in...
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Old 09-19-2012, 05:31 PM   #7
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Rpg heat exchanger blowing cold air


Does the inducer (small fan near the burners) run during a call for heat or not?!
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Old 09-19-2012, 06:04 PM   #8
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I turned it off at the fuse box waitef 30sec then restarted it. I blew in hoses unattached and attached. I heard click in the hose that goes to the fan but nothing in the hose that goes down to the metal box. The fan kicks on when you first start it up then turns off when the blower starts. Will this switch prevent me from seeing a flame in the see thru window?

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Old 09-19-2012, 06:27 PM   #9
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call a pro. You need a manometer to find the problem. A true professional should have and know how to use one.

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