How To Buy and Replace a Furnace Capacitor

By | September 14, 2020

install new capcitor2
Purchasing a furnace capacitor and installing it is easy to do and falls into the do-it-yourself category.

Basic precautions need to be taken mainly turning the power off to the furnace as not to get shocked.

Furnaces can fall into three categories when it comes to capacitors.

  • Not have a capacitor at all. Some units do not use a capacitors to run the blower motor.
  • Have two capacitors called a Start and Run capacitor.
  • Have only a single capacitor. This is the most common design type.
  • Where Is a Furnace Capacitor Located?
    To answer this question the panel door to the furnace will need to be removed.
    York furnace door

    The capacitor will be located close to the blower motor since it is there to help the blower motor run and have wires coming from it.
    motor
    furnace blower motor capacitor

    How To Read Your Capacitor Voltage And MFD for a Replacement
    Capacitors are rated by the voltage 120 volt, 220 volt, and the Micro Farads.

    Micro Farads are often abbreviated uf and sometimes MFD.

    To buy a new one the voltage and micro farad (uf) need to match. The packaging or size will only matter for fitting into the furnace.

    The side of the capacitor will have the voltage and uf on a label on its side.
    20140314_120415
    Here is a picture of a 5 uf, 370 volt capacitor. With these two numbers a replacement capacitor can be bought.

    Here is an example listed on Amazon
    Genteq GENTEQ – C305L / 27L570 GE Capacitor Oval 5 uf MFD 370 Volt 97F5705 (Replaces Old GE Z97F5705, 97F95702, Z97F5702), 5uf 370 Vac(VAC), 5X370 Run Capacitor

    As you can see it is rated for 5 Micro Farads (uf) and 370 volts. Any capacitor with the same voltage and micro farads can be used interchangeably.

    How Replace a Furnace Capacitor

    1. Turn off all power to the furnace.
    2. Locate the capacitor usual close to the furnace motor.
    3. How Replace a Furnace Capacitor

    4. Take pictures of the wiring to reference back if needed.
    5. Disconnect the wiring.
    6. Remove any bolt holding the old capacitor in place.
    7. Insert and bolt in new capacitor.
    8. Reconnect the wiring.
    9. Power on and test the system.

    Can a Furnace Capacitor Be Tested?
    Yes, testing capacitors are a part of heating and cooling troubleshooting and is done all the time. A multi-meter capable of reading Micro Farads will be needed. To learn how to test a capacitor click here.
    https://www.youtube.com/watch?v=4SY8lRl8HV0

     




     

One thought on “How To Buy and Replace a Furnace Capacitor

  1. Dennis

    Hello,
    Our air handler fan motor is not turning on, despite AC compressor unit working fine. I also tried turning on heat to see if this could start the fan (just to see if the fan motor is “alive”). Our air handler unit is for both AC and gas furnace. The fan blade turns easily (by hand).
    There is NO capacitor for the fan motor. The unit is a Trane from 2003. Could you suggest a few common culprits to look at?
    Thanks!,
    Dennis

    Reply

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