Hi guys,

My blower was making an awful whine so I bought a replacement and installed it but the controller blinks 3 lights which indicates that the pressure switch is stuck open. If I put the old one back it works without the error. Any ideas what would be wrong, or is it faulty or is the valve hole plugged in the new one? Doesn't look any different than the old one and don't know how to properly test it.

The unit I bought is an FB-RFB181, which matches the number on the old unit but the RPM is different; old is 3100, new is 3320 RPM.

Furnace is an Airco HDS 70/60.

Controller is a White Rodgers 50A55-843.

 

Was this an OEM ordered replacement? Restrictor plate and gaskets installed correctly?
You'd have to test it using a manometer.

 

It was a unit that was marked with the same part part numbers. Yes, gaskets and restrictor plate moved over from the old one.

Is there a way to test it without a manometer? That's something I don't have.

 

Not really, no.
I would prefer OEM parts, especially with things like inducers, as little differences can cause problems that will pull your hair out

 

So you reused the old parts. Any crack or tear in those parts will cause problems.

You can make your own manometer out of some cardboard and plastic tubing.
If you google manometer... there are many places that illustrate their construction and operation.

 

You need a good repairman to check this out for you, in my opinion.

You need a good repairman who has a good manometer and the knowledge of how to use it correctly.


\Most pressure switches need only very small pressures to close, and the pressures they are supposed to close at aren't usually readily available anyway.

A home constructed manometer isn't likely to be sensitive enough to measure the pressure you have with sufficient accuracy, and you aren't like to know the pressure you need anyway.

Unfortunately, there are plenty of repairman who can't do this test competently either.