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Wiring up a compressor + start kit


Wiring up a compressor
If there is an identifying mark on one side of the capacitor such as a Dash, Red paint or arrow pointing one direction that will be the run side of the capacitor, if no marks you can use either side for start or run.
If you have three terminals on the capacitor you have a dual capacitor, (C = RUN compressor and fan) (HERM = compressor start) and (FAN is fan start wire).
The Start wire goes to one side of the run capacitor it will be the only wire on that side of the capacitor.
The Run wire goes to the terminal side (T2) of the contactor, it will have another
wire from that terminal to the run capacitor which is the opposite side of the start wire.
The Common wire will go to the other side of the contactor (T1).
Start Kit
Start from the capacitor to terminal #1 on start relay There should be another wire from
here to start on the compressor.
Common from contactor (T1) to terminal #5 on start relay. There should be a wire from this terminal to the Common terminal on the compressor.(there will not be a capacitor in this circuit)
Run from the other side of the contactor (T2) to the start capacitor and from the other
Side of the start capacitor to terminal #2 on the start relay. There should also be a wire from this
Terminal to Run on the compressor.

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Replacing the Contactor on my Rudd AC model uaka-037jaz. I got a Dayton 2utl4 contator for a replacement. I need to know which wires connect to what location. I hooked it up with the 2 thermostat wires ar the marked 24 volt location. and the other wires as per the old contactor. It blew a fuse. Not sure of the wire locations as the item was not labeled. please help me find the post locations as to get this running. It is in the mid 90's, and the house is a tepid 88 degrees.


On this unit wiring is very basic, line in wires to the two lugs on the bottom, common as refered to is always black wire which goes to the compressor and the fan motor, red to adjacent lug of the contactor which then one goes to the capacitor and one to the compressor and one to the outdoor fan motor. One wire usually yellow from capacitor to start winding of compressor marked on the capacitor as herm, and a brown wire to the fan motor from the capacitor. The side connectors as you know go to the 24v control coil. The reason as to the fuse going out could be due to loose connections in the disconnect box or a short in the wiring at the compressor, fan motor or capacitor, and worst case a shorted compressor internally. Recommend having the system checked with the proper equipment to include an ohm meter with uf reading ability.

Aug 24, 2011 | Heating & Cooling

2 Answers

I have a Ruud Air Conditioner and need to install a new capacitor, but I forgot how the wires were on the old one. Can you help me in tellilng me which wire goes where.


There should be 3 terminals on the capacitor marked "C" "F" and "H".
A wire from the high voltage contactor goes to the "C".
Another wire from "C" goes to the compressor.
These wires are usually red.
The "F" terminal has a wire going to the fan,usually a brown wire.
The "H" has a wire going to the compressor,usually yellow.
There should be a wiring diagram on the control box cover identifying the terminals,colors and number of wires.

Jul 25, 2011 | Heating & Cooling

1 Answer

How do I wire a new condensor fan motor to the new capacitor? The old capacitor is longer and it has 3 terminals. the new capacitor is much smaller and oval. It has 2 terminals. the fan motor has 3 wires, black, brown, and purple. there is a red wire comming from the conductor and a yellow wire comming from somewhere else.


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.

Apr 05, 2010 | Heating & Cooling

1 Answer

I have a Trane XE1200 condensor for which I bought a replacement fan motor, same specs as the original G.E. motor. The original G.E. motor was wired to a dual capacitor, which is also wired to the compressor. The original G.E. motor had 4 wires, one of which was not hooked up. The replacement motor is an A.O. Smith model OAM10088 with 3 leads. Smith sent me a new 2-pole capacitor for the new motor. How do I wire it correctly?


OK, locate the terminals on the capacitor marked "HERM"(Compressor lead), "FAN", and "COM".(common)

HERM and COM remian as they are.

The wire going to "FAN" (usually brown) will be placed on either terminal of the new capacitor. (This is the ((usually brown)) wire comming off of the fan motor.) An additional wire needs to be run from the other terminal of the new capacitor to the "COM" on the old capacior.

What you are doing is bypassing the fan side of the old capacitor but still using the compressor side of the old Cap.

The fan should have a wiring diagram on it to help identify the wires if there is no brown wire. The other two wires will be identified on the wiring diagram as well, but one typically goes to the contactor and the other to the board.

Sep 07, 2009 | Heating & Cooling

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