If your air conditioner hums or fails to blow cold air, replacing a worn capacitor is a common fix. Always match the microfarad rating and check the voltage rating before picking a replacement.
Parts with these numbers
35+5 MFD 440/370V Round Dual Run Capacitor (Bluefin CPDRR1-355)
35+5 MFD 440/370V Round Dual Run Capacitor (Titan Pro TRCFD355)
35+5 MFD 440/370V Oval Dual Run Capacitor (Titan Pro TOCFD355)
- µF (MFD): must be the same, like 45/5
- Volts: same or higher (440 can replace 370)
- Shape: round or oval, to fit the bracket
What the Ratings Mean
Capacitor labels list capacitance in microfarads, which is written as µF, MFD, or uF. A 35/5 dual run capacitor supplies two separate ratings from one unit.
The larger number, 35 µF, powers the compressor through the HERM terminal. The smaller number, 5 µF, powers the outdoor fan motor through the FAN terminal. The C terminal serves as the common connection.
The voltage rating shows the highest voltage the capacitor can safely handle. A 440/370V rating means the capacitor is rated for 440 V and can safely replace an older 370 V or 440 V model. You can always use an equal or higher voltage rating, but never a lower one.
Reading the Label on Your Old Part
Look at the printed text on the side of your old capacitor can. You should see two numbers separated by a plus sign or slash, followed by MFD or µF.
Check the voltage listed beside or below the capacitance. If your old part says 370V, 440V, or 440/370V, this replacement will fit the electrical requirements.
- Look for 35+5 µF or 35/5 MFD.
- Verify the voltage rating is 370 V or 440 V.
- Note the physical shape of the can, which will be round or oval.
Comparing Shapes and Available Options
Round and oval capacitors with identical electrical ratings do the exact same job. The primary difference is how they mount inside the air conditioner compartment.
The Bluefin CPDRR1-355 is a round dual run capacitor rated at 35 + 5 µF and 440/370V. The Titan Pro TRCFD355 is also a round dual run capacitor with the same 35 + 5 µF and 440/370V ratings, and it replaces part number TRCD355.
If your system uses a flat bracket, the Titan Pro TOCFD355 provides an oval shape with 35 + 5 µF and 440/370V ratings. It replaces part numbers CAP-35/5/440 and CD35-5X440. Choose the shape that fits your mounting bracket and lets the wires reach.
Common Signs of a Failed Capacitor
When a run capacitor fails, the motors it powers cannot start or run properly. A fan that hums but will not spin is often caused by a bad capacitor rather than a broken motor.
The compressor may also fail to start, leaving the outdoor fan running while the system blows warm air inside. Physical signs of failure include a swollen top or bulging sides on the metal can.
How to confirm it fits
- Turn off power at the main breaker and the outdoor disconnect box.
- Read the capacitance rating on the old metal can to confirm it states 35 + 5 µF or 35/5 MFD.
- Confirm the old voltage is 370 V or 440 V, as this 440/370V part can replace both.
- Look at the mounting bracket to decide whether a round or oval can is needed.
- Take a photo of the wire connections before unplugging the old capacitor.
Questions
Can I use a 440 V capacitor to replace a 370 V capacitor?
Yes. A 440 V capacitor can safely replace a 370 V capacitor. Voltage ratings can be the same or higher, but you must never go lower.
What is the difference between round and oval capacitors?
Round and oval capacitors with the same ratings perform the same job. You should choose the shape that fits into your unit's mounting bracket.
What do the HERM, FAN, and C terminals connect to?
The HERM terminal connects to the compressor, the FAN terminal connects to the outdoor fan motor, and the C terminal connects to common.
Can I replace a 35/5 MFD capacitor with a different µF rating?
No. The capacitance rating in µF or MFD must match your old part exactly.
Related guides
Brand names and part numbers are used only to show fit. HVAC Fitter is not affiliated with, authorized by, or endorsed by any equipment maker. If you are not sure a repair is safe for you, call a licensed HVAC technician.