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Discussion Starter #1
Maybe somebody can please help me.
Somebody has previously tampered with my system and I'm trying to figure out some things.

The unit is an old Amana with AC and two stage NG furnace.
The indoor blower fan motor (115v) has a bunch of wires coming out of it.
(two for capacitor, two for motor reverse and black/white for AC)
The motor works when black/white are given AC.

BUT there are three more wires,
on the motor marked:

Blue : Med Hi
Yellow: Med Lo
Red: Lo

I believe that these three once upon a time plugged into an interface board, next to the furnace controller.

How do these control motor speed?
Do these lines get 115v or 24v?
What does the interface board actually do? (amana 20158901)

(The diagram on the unit just shows these wires going into interface board
without any specific locations on the board.....)

Any help unraveling this mystery would be appreciated.


Hvac Pro
23,688 Posts
There are 4 wires for 4 speeds. Black = Hi Blue=Med Hi Yellow=Med Lo Red=Lo. they get 115 volts. W/O seeing the diagram not likely we can help unless someone recognizes your unit. It should use another speed if it is a 2 stage unit unless some hacker altered it. Post some pics of it. Earlier units had an extra interface board to make them work as 2 stage and convert from 1 stage until they produced true 2 stage units. The part may be obsolete and someone backwards converted it.
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