How to Wire Up a Start & Run Capacitor

Written by jonra springs
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How to Wire Up a Start & Run Capacitor
Air conditioner compressors use start and run capacitors. (Comstock/Comstock/Getty Images)

Capacitors act like batteries to store power within electrical systems. The stored power is often used to add a boost of electric current to start a motor. Motors also use extra stored power while running at high speeds. Air conditioning systems use start-and-run capacitors for compressor motors. Air conditioning capacitors commonly wear out over time and have to be replaced. Neither a start capacitor nor a run capacitor is among the expensive parts of an air conditioner.

Skill level:
Moderate

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Instructions

  1. 1

    Turn off the air conditioner at the thermostat, and turn off the breaker switch for the outside unit before touching any of the wires inside.

  2. 2

    Connect the black power wire from the "T-1" terminal on the contactor inside the air conditioner unit to the potential relay terminal marked "5." Push the quick connectors on the wire ends on over the flat contacts on the relay and contactor terminals. The other black wire from the T-1 is connected to the "C" terminal on the compressor.

  3. 3

    Connect a striped wire from the "2" terminal on the relay to one of the three contacts on the terminal marked "Herm" on the dual run capacitor. Connect a blue or pink wire from the "S" terminal on the compressor to another contact on the "Herm" terminal of the capacitor.

  4. 4

    Connect a red power wire from the "1" terminal on the potential relay to either of the two terminals on the start capacitor. Wire the start-and-run air conditioning capacitors together by connecting another power wire from the other terminal on the start capacitor to one of the four connectors on the "C" terminal of the dual run capacitor.

  5. 5

    Connect the red power wire from the "T-2" terminal of the contactor to a contact on the "C" terminal on the dual run capacitor. Connect another power wire from another contact on the "C" terminal to the "R" terminal on the compressor.

Tips and warnings

  • Take note of the colours of the wires connected to the contacts on a run capacitor if you are replacing it. Plug the coloured wires back onto the same contacts on the new capacitor.
  • Replacing electrical components within an air conditioner is a job for a licensed electrician or certified HVAC repair agent. Do not attempt electrical work of this nature without the proper training and education.

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