I am replacing my old a/c fan motor with a new one. The old motor is an A.O Smith B13400-251 and has black, brown, and a purple wire and was connected to a dual capacitor. The new motor is an A.O Smith ORM5458 and has a white wire on one side and on the other is a black, brown, and a brown/white wire. The dealer sold us a single capacitor and i'm having a hard time figuring the wiring. Can anyone offer some instructions?

SOURCE: REPPLACING FAN AND COMPRESSOR CAPACITORS WITH A SINGLE UNIT

Well, it sounds as if you have a Coleman rooftop unit. If you have a start capacitor with a PTCR (Postive Temperature Coefficient Resistor) then it is different than if you have a Potential Motor Starting Relay. Why are you replacing the run and the fan capacitor?

Here is a link to the documentation that you need. If you do not have a Coleman and it is in fact a Duo-Therm, let me know the model number and I will be able to pull up the wiring schematic.

Thanks,

Jeff

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SOURCE: HELP!!! Help wiring new motor for CKL60-1

1. This is what your wiring should look like if you are using two caps. then you should be using a potential relay as well. This is the diagram for using a potential relay. Hope it helps you.

SOURCE: I am replacing the a/c

Motor Wiring
Old Motor
Brown wire is Start
Yellow wire is run or Power
Black wire is High Speed or Common
The other two taps are speed taps, but you have a single speed application
And high speed is what you need ,that’s why there’s not any wires
on Red and Blue if high speed was to much then you would move the
Black wire to one of the other taps RED low speed or Blue Medinm speed
New Motor
White goes to the Yellow wire from the capacitor
Black goes to the Black wire you took off of high speed on old motor
Of course both Brown wires go to the capacitor and Green to ground
If a capacitor doesn’t discharge it doesn’t mean it’s bad
but the capacitors don’t last as long as they used.
Any time you put in a new motor always replace the capacitor
It will save you a lot of time and grief later on.

SOURCE: how to wire motor to dual run capacitor

The easiest way to do it is to get a capacitor just for the fan motor (in the motor tag you can read what size cap. you need , maybe 5uf or 7.5 uf) and put the two brown wires on each side of the capacitor and the lines (probably white and black) to the contactor.

SOURCE: How do I wire a new condensor fan motor to the new

Before attempting any of these recommendations, First disconnect all the power sources and check your wiring diagrams on the motor and condensing unit.
On the old capacitor if you look on the top near each of the three terminals. Are they marked, fan - C - herm? If they are that is a dual capacitor and that needs to stay because that is also your compressor capacitor.
The Red wire from the conductor is Run and it's connected to C on the old capacitor.
Follow the Yellow wire and see if it goes to the S or start terminal on the compressor, if it does then that is the Start wire for your compressor and it connects to herm on the capacitor.
For the fan motor a lot of times the wiring connections are printed on the motor label.
Check the label, Purple should be run and connect to C on the old capacitor.
Black should be Common and it connects to the opposite side of the contactor as the Red wire. If the Red wire connects to T1 then the Black wire connects to T2.
The Brown wire shoud be the start wire on the fan motor and it connects to the Fan terminal on the old capacitor.
Now if you want to use the new fan capacitor. Take the Purple wire from the motor and look for any marks (red paint or a dash) on or beside the terminals on the new capacitor. If there is an identifying mark then connect the Purple wire to that terminal, if no marks you can connect it to either terminal. Then you need a jumper wire from C on the old capacitor to the purple side of the new capacitor. Then take the brown wire and connect it to opposite terminal of the new capacitor.