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mranswer, HVAC Mechanic
Category: HVAC
Satisfied Customers: 6157
Experience:  20 years experience running my own business
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I have a Ruud Deluxe 90 plus furnace will not ignite. When

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I have a Ruud Deluxe 90 plus furnace will not ignite. When I switch on the thermo the induction fan starts but will not close the pressure switch, if I disconnect any part of the vent pipe the switch will close and furnace will ignite reconnect vent and it shuts down.

Things I have checked

1) vent is clear with no obstruction
2) pressure switch is good
3) changed hose from fan to pressure switch
4) all condensation lines have been checked and are all clear
5) I can not find any intake pipe

M Oglesby :

Remove the rubber hose from the inducer fan motor.


M Oglesby :

Then use a paper clip to clean out the connection on the inducer fan motor that the rubber hose attaches to very good applying force if necessary. The paper clip should go all the way through touching the fan blades. Replace the hose when finished then attempt to turn the heat on.


Customer: Sorry Forgot to say I did that also hole is clear
M Oglesby :

Did you go on the rooftop to make sure nothing is blocking the vent pipe?


Customer: Vent exits through side wall and is clear
M Oglesby :

I will opt out so another expert can assist you because I am stomped.


You have either a bad pressure switch- it is simply taking too much suction to close it, or your inducer fan is not moving enough air to create a good draft - look for a corroded blower wheel. This is a process of elimination, so investigate as needed here and you will find the problem.
Customer: replied 4 years ago.
Installed new switch last night, and also had the fan off it looked clean
then something must be restricting the air flow- there may be a problem within the heat exchanger itself as you claim everything else is clear and unobstructed, so that is the only thing left here that would affect the draft.
mranswer, HVAC Mechanic
Category: HVAC
Satisfied Customers: 6157
Experience: 20 years experience running my own business
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