How to Replace a 35/5 Capacitor in Your AC Unit | Done Safely

Replace a 35/5 dual-run capacitor with power off, matching capacitance and voltage, and landing the three wires on HERM, FAN, COMMON as before.

You can replace a 35/5 capacitor in your AC unit yourself, and the job takes under an hour. The 35/5 rating means the part does two jobs at once in the outdoor condenser: 35 µF for the compressor and 5 µF for the condenser fan motor.

The swap is straightforward — kill power, discharge the old part, note the wiring, and move the wires to the matching terminals. Everything that goes wrong happens when someone skips the safety steps or substitutes the wrong rating.

Do This Before You Touch the Capacitor

The first rule is no power, anywhere. Kill the condenser at the breaker and, if your unit has one, the outdoor disconnect, then verify the circuit is dead with a multimeter or non-contact voltage tester before opening the panel.

A dual-run capacitor can hold a shock-hazard charge for a while after power is removed. Short the three terminals together with the blade of an insulated screwdriver to discharge it before you handle the part.

Photograph the capacitor and wiring first so every wire’s original position is on record. Stop and call a certified HVAC technician if the label is unreadable, the part uses an unusual form factor, or you see corrosion or burnt wiring.

One boundary matters here: a capacitor swap is electrical work, not refrigerant work. If the repair starts involving sealed refrigerant lines, Section 608 rules under the Clean Air Act prohibit venting refrigerant during maintenance or service, and that work belongs to a certified technician.

The Step-by-Step Swap for a 35/5 Capacitor

Most residential condensers use the same three-terminal layout — HERM for the compressor, FAN for the fan motor, and COMMON for the shared return — so installation is a straight wire-for-wire move.

1. Confirm the condensing unit is off at the breaker and the outdoor disconnect, then verify zero voltage at the unit before opening it.
2. Discharge the old capacitor by shorting the three terminals together with an insulated screwdriver blade.
3. Photograph or label the wires, pull them off HERM, FAN, and COMMON, then remove the old capacitor from its bracket.
4. Set the new 35/5 capacitor in the same position and reconnect each wire to the terminal it came from — do not swap HERM and FAN.
5. Close the access panel, restore power at the disconnect and breaker, and watch the condenser start.

If the fan spins up and the compressor kicks on without humming or tripping the breaker, the replacement worked.

What’s the Correct 35/5 Replacement?

The replacement must match the original capacitance exactly — 35/5 µF — with a working voltage rated equal to or higher than the old part.

Common voltage ratings are 370 VAC, 440 VAC, and 450 VAC. A 35/5 rated at 440V or 450V can replace a 370V original, and a 450V part can cover a 440V unit; a 370V part is only safe on a 370V system.

Most replacements are round dual-run capacitors with three terminals on top, about 4-5/8 inches high and 2 inches wide. The same electrical rating is a universal replacement across HVAC brands and can cover multiple OEM part numbers — as long as capacitance matches, voltage is equal or above, and the part fits the mounting.

If you’re ready to order, our roundup of the best 35/5 capacitors compares common form factors and voltage ratings side by side.

The failures that kill capacitors fast are the shortcuts: wrong µF, lower voltage, mixed-up terminals, or skipping power isolation and discharge. Any of these can damage the new part or the compressor, so match the numbers and take the 30 seconds to discharge.

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