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can someone help me understand the logic of Nordyne Tappan Ra 80 Furnace defect

can someone help me understand the logic of Nordyne Tappan Ra 80 Furnace defect


  #1  
Old 12-22-11, 04:39 PM
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can someone help me understand the logic of Nordyne Tappan Ra 80 Furnace defect

Nordayne Tappan Ra 80 horizontal unit, residential, gas, 10 yrs. old.
The unit was working fine this winter, however was not staying on continisuly until reaching desired temp. was stopping and then restarting again and achived desidered temp. Then it finally stop working yesterday, inducer fan comes on only and was getting 3 flashing red lights. (pressure switch stuck open)
Changed the flame sensor and installed a new Pressure switch .55 psi.. It worked fine for 1-2 hours, and now inducer fan is on, igniter comes on, then gas valve opens, and immedialy closes, with three flashing red lights again (pressure switch stuck open, i think). and the cycle starts over again, and again.
Reset by cutting power for 5-10 min. works for a hour and problem persists.
Checked the piping all way to the roof, free of any obstuctions.
Any Idea on the Logic?
 
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Old 12-22-11, 05:36 PM
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Don't guess. Usually there is a list of codes on the furnace, often inside the fan compartment door. What does it say?


If that is the correct explanation for that diagnostic code, I'd use a multimeter set to the ohms scale to determine whether the pressure switch is opening after the furnace shuts off.

If it is opening and the circuit board says it isn't you will need to replace the circuit board.
 
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Old 12-23-11, 07:21 AM
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I just verified the dignostic code, 3 blinks is pressure switch stuck closed......you'r right, never guess!
The switch is new, now i'll check with the multimeter.
Thank you for your help
 
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Old 12-23-11, 02:08 PM
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Bingo!!!!!!!!!!
I just found the little rubber pipe from the pressure switch to the inducer to have a little cut on it cousing a pressure leak trigging the pressure switch to close.
I replaced that pipe and my unit is working like a charm... (keeping up for 3 hrs now) Lets hope this is it!!!!!!!! Happy warm Holidays everyone
 
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Old 01-05-12, 10:51 AM
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Actually, It end up being a bad circuit board, I replaced it with a new one, $129.00 and it is now working fine without a hitch. Thank you for your advice Seattlepioneer! right -on
 
 

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