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HVAC Help! pressure switch stuck open.

6K views 5 replies 5 participants last post by  secretsneeper 
#1 · (Edited by Moderator)
Inter-city forced air furnace.
Cycles without firing. Error code 3 on white rodgers universal controller board (50a55-843).

Error code three is open pressure switch.

Manual manipulation of switch will repeat will allow furnace to run. When running high limit switches stay repeat stay in functioning resistances.

Problem seems to be the "pull back" on pressure switch. Diaphragm is repeat is good.

My gf is preggers and this is her furnace, 7 months into it so she def needs heat! Haha.Thank you.

 
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#3 ·
Remove the long black hose from the draft inducer motor (the black hose that connects to the pressure switch, pressure switch being upper right) and softly suck and blow on it. Listen for the distinct click in the pressure switch. This should help unstick the mechanism.

Also, remove the black hose from the pressure switch itself and wiggle an unfolded paper clip around in the port.
 
#4 ·
keep in mind the control board needs to see an action stat calls ID comes on and then the PSI closes indicating ID air...if you force it it will fail and you need to repower to do a restart with no jumps.....the board stores the failures on the ID....pressure switch failures.clear the switch or change it with no power then test on that repower and tube connected
 
#6 ·
Tator1076 - thanks bud. im actually jumping the high limit on the board and using a multimeter to check that it is not giving an infinite resistance.

biggles - u sound very knowledgeable, unfortunately i only understand about half of what u said.

Doc Holliday - yes sir i have verified the action of the pressure switch itself, the problem exists in that it is not drawn back by the furnace pressure once it is on the appropriate cycle.

beenthere - sorry bud, wont do it again.
 
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