Electrical
Capacitor and Contactor Field Checks
A fast reference for the two outdoor-unit failures you can lose a day on if you skip the basics.
Capacitor checks
- Kill power and discharge safely before measuring capacitance.
- Compare each section of a dual capacitor to the label rating, not to the other side of the can.
- Swollen tops, oil residue, and heat discoloration mean replace it even before the meter does.
Capacitor call
| Condition | Interpretation | Action |
|---|---|---|
| Within rating | Cap may still be serviceable | Continue to amperage and voltage-drop checks |
| More than 6% low | Weak start/run support | Replace |
| Open or shorted | Failed part | Replace and inspect the motor it supports |
Contactor checks
- Confirm 24V at the coil before condemning the contactor.
- Inspect line and load side for burned lugs, loose terminations, and measurable voltage drop.
- If contacts are welded, check whether the compressor or fan motor overamped and cooked the points.