How-To Wire Condenser Fan Motors Properly in 3-Wire & 4-Wire Configurations | Dreisilker Electric Motors

“my original condenser fan motor has three wires and the replacement condenser fan motor I bought has four wires. Did I buy the wrong engine?”

This is by far the most common post-transaction question we receive from customers who have recently purchased replacement condenser fan motors. Bottom line, no you didn’t buy the wrong condenser fan motor. While most original condenser fan motors only have three wires, it is very common for aftermarket condenser fan motors to have four. This guide will explain how to wire up your new condenser fan motor using either a four-wire configuration or a three-wire configuration when using a single run capacitor or dual run capacitor.

a review of the components:

If you recall from our residential cooling season guide, outdoor condenser units use a switch called a contactor. This switch is controlled by the thermostat and closes to complete an electrical circuit when power needs to be supplied to the compressor and condenser fan motor. Think of the contactor almost like a gatekeeper: two legs of 115-volt power supply must flow through it for your system to work properly.

Condensing units also use a component called a run capacitor. Run capacitors allow condenser fan motors and compressors to run more efficiently and are rated by a unit of measurement called microfarads. dual run capacitors are used for both the condenser fan motor and the compressor. single run capacitors are used exclusively for the condenser fan motor or only for the compressor. Just like your contactor, your capacitor must be wired correctly to work properly.

using a dual run capacitor:

if you are using a dual run capacitor, you will only be using three of the four wires coming out of the new condenser fan motor.

You are going to connect the black wire where the black wire from the previous condenser fan motor was connected. this is likely going back to your contactor. you are going to connect the white wire to where the white wire from the previous condenser fan motor was connected. this will probably be the “c” or “common” terminal on your dual run capacitor. finally, you will connect the brown wire to where your previous brown wire was connected. this will probably be the “f” or “fan” terminal on your dual run capacitor. the brown wire with the white tracer will not be used for this configuration. you can use a wire nut and electrical tape to tie it down.

note: you will need a jumper between the “c” or “common” terminal of the capacitor and one leg of the contactor.

using a single-run capacitor with a four-wire configuration:

If you purchased a new condenser fan motor with a new single run capacitor, this will be the wiring configuration you will use. you are going to connect the black wire to where the black wire from the previous condenser fan motor was connected. this is likely going back to your contactor. you are going to connect the white wire to the other leg of your contactor. you are going to connect the brown wire to one set of terminals on your new capacitor and you are going to connect the brown wire with the white tracer to the other set of terminals.

using a single-run capacitor with a three-wire configuration:

If you bought a new single run capacitor and the condenser fan motor you are using only has three wires coming out of it, this is the wiring configuration you will use. you’re going to reconnect the black wire to where it was previously connected. this is likely going back to your contactor. you are going to connect the white wire to a set of terminals on your new capacitor. you will need to connect a jumper from this set of terminals to the other leg of your contactor. Finally, you’ll connect the brown wire to the opposite set of terminals on your new run capacitor than the common wire.

summarize everything:

There’s always a sense of satisfaction in completing a project yourself, but hooking up a new condenser fan motor and run capacitor can be a bit tricky if you haven’t done it before. safety is always the top priority. make sure the electrical supply to the condenser unit is switched off before starting any work. use your multimeter to confirm the disconnection. If you’re not comfortable working with electricity, contact a local HVAC contractor and they’ll be happy to complete this task for you.

It is very helpful to document the location of the existing wire connections before removing the condenser fan motor or run capacitor. use a camera to take pictures of the connections and refer to the pictures when installing the new condenser fan motor and run capacitor.

For a visual image of typical wiring configurations, please refer to the following guide: hvac condenser fan motor wiring diagram.

Finally, this guide is designed to be used as an overview of common condensing unit wiring schematics. Some condenser fan motors plug into a circuit board, while others use proprietary plugs for their connectors. We strongly recommend consulting your unit’s manual for proper wiring instructions.