Replace a Run Capacitor

Power off, bleed the cap, match µF + voltage, land HERM/FAN/C correctly, verify.

Approx. 25 min

Before you start

•Confirm the symptom points to the capacitor (hum on call, fan won't start, weak/no compressor, bulged or leaking can).
•Know whether it's a single round capacitor or an oval dual-run (HERM + FAN + common C).
•Have the replacement on the truck: same µF (both values on a dual) and equal-or-higher voltage rating.

Tools & materials

Insulated screwdriver · Multimeter with capacitance (µF) function · Needle-nose pliers · Replacement capacitor (matched µF, ≥ rated VAC) · Phone camera (photo the wiring before you touch it)

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Isolate & make safe

Kill power at the disconnect and breaker
Pull the disconnect at the condenser and switch off the breaker. Verify 0 V across L1–L2 with your meter before opening the panel.
Tools: Multimeter
⚠ Lockout/tagout. Never trust the disconnect alone — verify zero volts with a meter.
Discharge (bleed) the capacitor
Even with power off, a capacitor stores a charge. Discharge across each terminal pair (and each terminal to common on a dual-run) using a 20k–50k Ω resistor or an insulated screwdriver as a last resort.
Target: Confirm <1 V across the terminals after bleeding
⚠ A charged run capacitor can deliver a painful, dangerous shock. Bleed it and confirm 0 V before touching the terminals.

Remove & match

Photograph and label the wiring
Photo the existing leads before removing anything. On a dual-run, identify HERM (compressor), FAN (condenser fan motor), and C (common, line side).
Read the old can and (if possible) test it
Record the printed µF and voltage. If the can isn't blown, read it on the meter's capacitance setting after bleeding.
Target: A failed cap typically reads more than ±6% off its rated µF (or open/shorted)
Match the replacement
Use the same µF on each side of a dual-run (e.g. 45/5). Voltage rating must be equal or higher (a 440 VAC cap can replace a 370 VAC; never the reverse).
Target: µF exact; replacement VAC ≥ original VAC

Install & verify

Land the leads on the new capacitor
Wire HERM, FAN, and C back exactly as photographed. Seat the strap so the can can't vibrate loose.
Confirm the new cap's value before energizing
Bleed (it ships uncharged, but confirm) and meter each section on the capacitance setting.
Target: Within ±6% of the printed rated µF on each section
Restore power and confirm operation
Re-energize, call for cooling, and confirm the condenser fan and compressor start promptly with no hum. Clamp the run amps and compare to the nameplate RLA.
Tools: Clamp meter
Target: Compressor running amps ≤ nameplate RLA; fan within FLA