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 so 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 capacitor 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.
- Turn off all power to the furnace.
- Locate the capacitor usual close to the furnace motor.
- Take pictures of the wiring to reference back if needed.
- Disconnect the wiring.
- Remove any bolt holding the old capacitor in place.
- Insert and bolt in the new capacitor.
- Reconnect the wiring.
- Power on and test the system.
Where Is a Furnace Capacitor Located?
To find the furnace capacitor, the panel door to the furnace will need to be removed.
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.
How To Read Your Capacitor Voltage and MFD for a Replacement
HVAC capacitors are rated by the voltage and the Micro Farads.
Micro Farads are usually 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.
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 to Replace a Furnace Capacitor
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.
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