How to Replace the Motor Start Capacitor on a Samsung Dishwasher

The motor start capacitor provides the initial electrical boost that gets the circulation pump motor spinning. When it fails, the motor hums (you can hear it energize) but cannot start rotating. This presents as a dishwasher that fills with water normally, hums loudly during the wash phase, but never produces spray arm rotation. After several seconds of failed starting, the motor's thermal overload trips and the humming stops. This cycle may repeat throughout the wash phase: hum, stop, hum, stop.

This symptom is commonly misdiagnosed as a circulation pump motor failure, leading to expensive and unnecessary pump replacement. A capacitor costs $8-$25 and takes 15 minutes to replace, versus $100-$250 for a new circulation pump. Always test the capacitor before condemning the motor.

Before You Start

• Tools needed: Phillips #2 screwdriver, multimeter with capacitance mode (or a dedicated capacitor tester), insulated screwdriver for discharge, needle-nose pliers
• Parts needed: Motor start capacitor (~$8-$25, match microfarad rating exactly)
• Time required: 15-25 minutes
• Difficulty: Intermediate
• Safety warning: Capacitors store electrical charge even after power is disconnected. Discharge the capacitor before handling by shorting the terminals together with an insulated screwdriver (hold by the insulated handle). Disconnect power at the circuit breaker AND wait 5 minutes before starting work.

How to Confirm the Capacitor Has Failed

Symptom Pattern

The key diagnostic pattern for a failed start capacitor:

1. Dishwasher fills with water normally (fill valve works)
2. After fill, you hear a loud hum from under the tub (motor trying to start)
3. No spray arm rotation (motor cannot overcome starting torque without capacitor)
4. Hum continues for 5-15 seconds then stops (thermal overload trips)
5. After a pause, hum resumes (overload resets, motor tries again)
6. Drain pump works normally at end of cycle (drain pump has its own smaller motor)

If this matches your dishwasher, the capacitor is the prime suspect.

Capacitor Testing with Multimeter

1. Disconnect power at breaker. Wait 5 minutes.
2. Remove kick plate (two Phillips screws + two plastic clips).
3. Locate the start capacitor. On Samsung dishwashers, it is a small cylindrical or oval component (approximately 1-2 inches long) mounted on the frame near the circulation pump motor. It has two wire terminals (push-on spade connectors) and is labeled with its microfarad (uF) rating (commonly 3, 4, 5, 6, or 8 uF for Samsung dishwashers).
4. Discharge the capacitor: touch an insulated screwdriver blade across both terminals simultaneously. You may see a small spark (this is normal and harmless).
5. Disconnect both wires from the capacitor terminals.
6. Set your multimeter to capacitance mode (often marked with the capacitor symbol or "F" for Farads).
7. Measure across the two capacitor terminals.
8. Compare the reading to the labeled rating:
   • Within 10% of labeled value = good capacitor (problem is elsewhere)
   • Significantly low (under 50% of rated) = weak capacitor, replace
   • Reading of 0 = shorted capacitor, replace
   • OL or no reading = open capacitor, replace

Alternative Test Without Capacitance Mode

If your multimeter lacks capacitance mode:

1. Set to high ohms range (200K or higher).
2. Touch probes to capacitor terminals.
3. A working capacitor will show resistance rising from low to high (as it charges from the meter's battery). The reading climbs over several seconds.
4. A dead capacitor shows either OL immediately (open) or 0 permanently (shorted).
5. This test is less definitive than capacitance mode but indicates whether the capacitor is completely dead.

Step-by-Step Replacement Instructions

Step 1: Disconnect Power and Discharge

Turn off circuit breaker. Wait 5 minutes. Remove kick plate. Locate and discharge the capacitor as described above.

Step 2: Note the Capacitor Specifications

Before removing the old capacitor, record:

• Microfarad rating (e.g., 6 uF, 8 uF)
• Voltage rating (e.g., 250V AC, 450V AC)
• Physical dimensions (for fit in the mounting bracket)

The replacement must match the microfarad rating exactly. Voltage rating can be equal or higher (never lower). A 250V-rated capacitor can be replaced with a 450V-rated unit of the same microfarad value, but not vice versa.

Step 3: Remove the Old Capacitor

The capacitor is mounted in one of these ways:

• Bracket with screw: A metal bracket holds the capacitor against the frame. Loosen or remove the screw and slide the capacitor out.
• Clip mount: A plastic or metal clip snaps around the capacitor body. Squeeze or pry the clip to release.
• Cable tie: Some Samsung models secure the capacitor to a wire harness or frame member with a plastic cable tie. Cut the tie with scissors.

Pull the spade connectors off the capacitor terminals. They may require a slight wiggle. Note which wire goes to which terminal (though capacitors are not polarity-sensitive for AC motors, consistent wiring helps).

Step 4: Source the Replacement Capacitor

Samsung does not always sell the capacitor as a separate part. Options:

• Search Samsung Parts by your model number for "capacitor" or "start capacitor"
• Search appliance parts retailers (RepairClinic, AppliancePartsPros) by model number
• Purchase a generic motor run/start capacitor from an electrical supply house matching the exact uF and minimum voltage rating. The physical form factor (cylindrical vs. oval) must fit the mounting bracket.

Common Samsung dishwasher capacitor values: 4 uF/250V, 6 uF/250V, 8 uF/450V.

Step 5: Install the New Capacitor

Mount the new capacitor in the bracket/clip/tie-down. Push the spade connectors onto the new capacitor terminals firmly. Ensure the connectors grip tightly (a loose connector will arc and burn).

Step 6: Test Before Reinstalling Kick Plate

Restore power. Run a Normal cycle. Listen during the wash phase start:

• With a working capacitor, the motor should start within 1-2 seconds of energizing (brief hum followed by smooth running sound and spray arm whooshing).
• If the motor still only hums, the motor itself has failed (bearings seized, winding shorted) and needs replacement.

Step 7: Reinstall the Kick Plate

Once confirmed working, reinstall the kick plate with screws and clips.

Understanding Why Capacitors Fail

Motor start capacitors fail due to:

• Age: Electrolytic capacitors dry out over 5-10 years. The dielectric fluid evaporates slowly, reducing capacitance until the motor cannot start.
• Heat: Located near the motor, capacitors endure temperature cycling. Excessive heat accelerates fluid evaporation.
• Power surges: Voltage spikes can puncture the dielectric film, creating a short circuit.
• Overloading: If the motor has been struggling to start (due to a partially jammed impeller), the capacitor handles excess current and degrades faster.

Samsung Dishwasher Models and Typical Capacitor Values

Always verify with the label on your specific capacitor rather than relying on model-based lookup.

When to Call a Professional

• You are not comfortable working with capacitors (stored charge can cause painful shock)
• The motor still does not start after capacitor replacement (motor itself has failed)
• You cannot locate the capacitor in your dishwasher (some newer models integrate it into the motor housing)
• The motor's thermal overload is tripping repeatedly (potential wiring short or motor ground fault)

Cost Comparison: DIY vs Professional

Need Professional Help?

• Dishwasher repair service
• Samsung appliance repair
• Dishwasher repair cost guide

FAQ

Q: Is it safe to replace a dishwasher motor capacitor myself? A: Yes, with proper precautions. Discharge the capacitor before touching terminals (short them with an insulated screwdriver). Disconnect power at the breaker and wait 5 minutes. The voltage stored in a dishwasher capacitor (typically 120-250V) can deliver a painful shock but is not typically dangerous for a healthy adult. Still, discharge first every time.

Q: Can I use a higher microfarad capacitor than the original? A: No. Using a higher microfarad value than specified can over-torque the motor at startup, potentially damaging the motor windings or impeller shaft. Always match the exact microfarad rating. Voltage rating can be equal or higher, but never use a higher capacitance value.

Q: How do I know if the problem is the capacitor or the motor? A: If the motor hums but won't start, try spinning the motor manually (through the sump with the filter removed, push a spray arm mount or impeller with a long screwdriver). If the motor starts running once given a manual push-start, the capacitor is dead but the motor is fine. If it still won't run even with a push-start, the motor has failed.

Q: My Samsung dishwasher hummed then now makes no sound at all. What happened? A: The motor's thermal overload has permanently tripped (or the motor winding burned out from repeated stalled starts). If a burned smell accompanies the silence, the motor winding has shorted. If you only smell normal dishwasher odor, wait 30 minutes for the thermal overload to reset, then try again. But at this point, the capacitor (and potentially the motor) needs replacement regardless.

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