ruud furnance upgh-12earjr wont ignite


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Old 04-16-12, 04:22 PM
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ruud furnance upgh-12earjr wont ignite

Hi
i have a ruud furnace part# upgh-12earjr that wont ignite. I have a working inducer motor, working blower motor and i "think" a closing pressure switch although i am not certain. I know it is getting 24 vdc howver. I replaced the ignitor assembly and still no flame. I know gas is flowing from the switch because i hear it click and then smell gas flowing to where the burners are. What could it be? Do we have a bad thermostat? Is there a way to bypass something to isolate the problem?

thank you
 
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Old 04-16-12, 04:57 PM
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What type of ignition system is on the furnace? Is it a "glow plug" (properly called Hot Surface Ignition), spark to pilot, or spark to main burner?
 
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Old 04-16-12, 05:32 PM
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ignitor type

Its what they call a direct spark ignitor. kind of looks like a tuning fork.
it has the ceramic cylinder with a metal piece in the middle and two metal leads coming from it on one end and then the wire that goes to the IFC on the other end.
 
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Old 04-16-12, 05:32 PM
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Does the ignitor glow or spark? As Grady asked we need to know that info to tell you what to check. BTW, the furnace operates on 120V and 24V AC, not DC.
 
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Old 04-16-12, 06:13 PM
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ignitor

The ignitor appears to spark at least once when it is operating. I am sorry if it wasnt clear before the 24 vdc was for the pressure switch, not the furnace itself. the ignitor never glows that i can tell. the inducer just keeps running and so does the blower fan. i also noticed that the 24 volts applied to the pressure switch is for a very short time as the inducer fan gets going and then goes to 0 volts. I assume that is normal but wanted to ask.
 
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Old 04-16-12, 06:20 PM
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again, your furnace does not use DC! EVEN YOUR PRESSURE SWITCH. All AC, NO DC. Where are you measuring voltage? If you are measuring voltage across the pressure switch then that sounds normal. What you have described sounds like you need a new control board.
 
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Old 04-16-12, 06:41 PM
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new ifc

Right, it is all AC. sorry i did have it on volts ac when i measured that. Anyway, why do you think it is a bad controller board? theres three leds on the board. both appear solid green when the unit is on. The third one that says "flame" never turns on and that is an orange led. i assume that doesnt go on since the burners never ignite. THe thing is, shouldnt i be seeing some kind of blinking sequence or something if the board was in partial failure? Since the inducer motor still runs and the blower runs is it really just a bad board? are there some voltages i can check for on the board to determine if that is true?

Also, how do i know something isnt blocked or the vents have an issue? I have an evap coil sitting on top of my unit for my air conditioner. Could there be a blockage in there?

Sorry with all the questions but i assume that a IFC replacement is very expensive to replace so i want to know if there is way to know if it is shot.

thanks
 
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Old 04-17-12, 03:55 AM
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You should hear a lot of sparking when the gas valve opens. The gas valve won't open unless the pressure switch closes indicating all other safeties have passed their test as well.
 
 

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