How do I stay safe before testing?
A capacitor stores electrical energy and can hold a dangerous charge even when the pump is unplugged. Treat every capacitor as live until you have discharged it.
- Switch the pump off and isolate the power at the breaker at the switchboard. Don’t rely on the wall switch alone.
- Open the motor terminal cover and locate the capacitor (usually a cylindrical can, sometimes inside a separate housing).
- Discharge the capacitor by bridging its two terminals with a bleed resistor (around 10-20 kΩ, 5 W) or a proper capacitor discharge tool. A bare insulated-handle screwdriver across the terminals also drains it but sparks violently and can pit the terminals, so use that only as a last resort. You may hear or see a small spark: that’s the stored charge leaving.
- Wear safety glasses and keep one hand in your pocket while working near terminals.
In New Zealand, fixed mains wiring must be done by a licensed electrician. Testing and swapping a plug-in capacitor on a portable appliance is generally fine for a DIYer, but if you’re unsure or the pump is hard-wired, use an electrician.
What do I need to test a capacitor?
- A multimeter with a capacitance (µF) range: a continuity-only meter won’t give you a number.
- Insulated screwdriver and a discharge resistor.
- A photo of the capacitor’s printed label before you start.
What should I read off the label first?
Every capacitor has its rating printed on the side, for example “35 µF” and a voltage like “450V”. Note the microfarad (µF) value, the voltage, and the tolerance (often ±5% or ±6%). This printed µF is your reference: a healthy capacitor should measure close to it. Never guess the value from the pump model; always go off the label on your own part. If the label has worn off, the capacitor cross-reference guide shows how to work from the OEM part number instead.
How do I test a pump capacitor with a multimeter?
- Confirm the power is off at the breaker and the capacitor is discharged (see the safety section above).
- Disconnect at least one of the capacitor’s wire terminals so the motor windings don’t affect the reading. Note where each wire goes (take a photo).
- Set your multimeter to capacitance mode (the µF or “‑||‑” symbol). Auto-ranging meters pick the scale for you; on a manual meter select a range above the printed value.
- Touch the probes to the two capacitor terminals. Polarity doesn’t matter: film run capacitors (CBB60/CBB65) and CD60 start capacitors are both non-polarised AC parts.
- Wait for the reading to settle: it may climb for a second or two as the cap charges from the meter.
- Compare the settled reading to the printed µF.
What do the multimeter readings mean?
Compare the settled reading on your meter against the µF printed on the capacitor:
| Meter reading |
Verdict |
What to do |
| Within printed tolerance (a 35 µF ±5% cap reads 33.25-36.75 µF) |
Healthy |
Capacitor is fine: look elsewhere for the fault |
| Noticeably low (e.g. a 35 µF cap reads 26 µF) |
Weak / failing |
Replace it |
| Near zero, “OL”, or never settles |
Open / dead |
Replace it |
| Zero with continuity, or visibly bulged, leaking or domed on top |
Shorted |
Replace, never reuse a bulged cap |
If the number is good but the pump still misbehaves, the fault is likely elsewhere (windings, centrifugal switch, wiring, or the pressure/impeller side).
How do I choose a replacement capacitor?
Match the µF and voltage to your old capacitor, or to the motor nameplate. It’s fine to fit a capacitor with an equal-or-higher voltage rating, but keep the µF the same. The wrong capacitance stresses the windings and can damage the motor.
- Film run capacitors are marked CBB60 or CBB65.
- Electrolytic start capacitors are marked CD60.
Learn more on our pump capacitors guide, or let the find your capacitor wizard match the right part to your pump.
Frequently asked questions
What multimeter reading means a capacitor is bad?
Compare the settled reading with the µF printed on the label. A reading within the printed tolerance (often ±5%) is healthy. A reading noticeably below the label means the capacitor is weak; near zero, “OL” or a reading that never settles means it’s dead. Replace it in either case.
Do I need to disconnect the capacitor to test it?
Disconnect at least one of its wire terminals so the motor windings don’t affect the reading, and photograph where each wire goes first. Isolate the power at the breaker and discharge the capacitor before you touch the terminals.
Can I test a capacitor with any multimeter?
You need a multimeter with a capacitance (µF) range. A continuity-only meter won’t give you a µF reading.
Does polarity matter when testing a capacitor?
No. Motor capacitors are non-polarised AC parts: film run capacitors (CBB60/CBB65) and CD60 electrolytic start capacitors alike, so either probe can go on either terminal.
The capacitor tests fine but the pump still won’t run properly. What next?
If the reading is within tolerance, the fault is likely elsewhere: the motor windings, the centrifugal switch, the wiring, or the pressure or impeller side of the pump.
Get the right part
Tell us your µF, voltage and body code and we’ll point you to the exact match. Start with the find your capacitor wizard, or browse pool pump capacitors.
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