Note, this article is created with ChatGPT and edited by AVA.
Understanding start capacitors in pressure washers
(For AVA users and other brands)
Start capacitors are small but essential components in electric pressure washers with single-phase induction motors. Without a working capacitor, the motor may fail to start, emit a humming sound, or trip a fuse.
This guide explains:
- What a start capacitor does
- How to recognize failure symptoms
- How to test and safely replace one
- AVA-specific notes (Master, Master 2.0, Evolution, V6)
What Is a start capacitor?
A start capacitor temporarily stores electrical energy and releases it during motor startup to provide the extra torque needed to begin rotation. It works similarly to a battery in concept: a two-terminal component that stores energy for short bursts.
Key characteristics:
- Non-polarized – can be installed in either direction
- Rated in microfarads (µF) – typically 25–50 µF in pressure washers
- Disconnects automatically after motor reaches running speed
In AVA machines like the Master P60/P70, Evolution P60/P70, and V6 P70, a 35 µF start capacitor is mounted directly to the motor housing.
What causes capacitor failure?
Capacitors are wear parts and can degrade over time. Common causes include:
| Cause | Description |
|---|---|
| Aging | Internal electrolyte dries out with time |
| Heat | Prolonged motor use or hot environments |
| Voltage drops | Often due to long extension cords, thin wiring (e.g. in garages or boathouses) |
| Power surges | Lightning or sudden current spikes |
| Mechanical overload | Jammed motor or pump blockage |
Even though AVA washers are protected by an internal thermal switch, external issues (e.g. bad wiring or unstable voltage) can damage the capacitor.
Symptoms of a Faulty Capacitor
Your pressure washer may have a bad capacitor if:
| Symptom | Likely Cause |
|---|---|
| Hums but doesn’t start | Capacitor failure, stuck rotor, or low voltage |
| Starts only when you spin the motor manually | Weak capacitor |
| Tripped fuse or breaker when starting | Shorted capacitor |
| Bulging or leaking capacitor | Physical damage – replace immediately |
| Humming sound in standby mode but still starts | Likely a pump issue, not the capacitor |
How to test a capacitor
Method 1: With a Multimeter (Capacitance node)
- Power off and unplug the machine.
- Discharge the capacitor safely (e.g., using a resistor).
- Remove at least one wire terminal from the capacitor.
- Set multimeter to capacitance mode (–|(-- symbol).
- Connect probes to terminals.
- A good 35 µF capacitor should read within ±5–10% of its rating.
Method 2: Resistance test (Ohms mode) – For basic multimeters
- Set to resistance mode (Ω)
- Connect probes to capacitor terminals
- Look for the needle or display to:
- Start low, then gradually rise to infinite → Good
- Stay at 0 Ω → Shorted, replace
- Stay at ∞ Ω → Open circuit, replace
- Reverse probes and repeat
Also check for visible signs of failure: swelling, cracks, fluid leakage.
How to Replace a Start Capacitor – Safely
Capacitor replacement is simple and safe if you follow precautions:
Safety Checklist:
- Unplug machine completely
- Discharge old capacitor
- Use insulated tools and gloves
- Mount replacement securely
- Reconnect all terminals correctly
- Reattach grounding wires to clean metal
Click here to read our article regarding safety
For AVA machines, follow these service guides:
- Replace capacitor – Master Series
- Replace capacitor – Evolution Series
- V6 P70: Use Evolution guide as reference.
Using a Third-Party Capacitor
You can use a non-original capacitor if it matches these specs:
| Parameter | Requirement |
|---|---|
| Capacitance | Exact match (e.g. 35 µF) |
| Voltage rating | Equal or higher (e.g. 400–450V AC) |
| Type | Motor-grade (not for audio or lighting) |
| Tolerance | ±5% preferred |
Do not use:
- Wrong capacitance (e.g. 25 µF instead of 35 µF)
- Lower voltage ratings
- No clear label or technical documentation
Summary Table
| Symptom | Possible Cause | Action |
|---|---|---|
| Humming, no start | Capacitor failure, low voltage, or blockage | Test capacitor |
| Starts only when pushed | Weak or marginal capacitor | Replace |
| Tripped fuse | Shorted capacitor | Replace immediately |
| Visible damage | Physical failure | Replace |
Final Tips
- Always inspect power supply quality — poor wiring often damages capacitors
- If one component fails, others may be stressed – test all relevant parts
- AVA original capacitors are available on our website.
-
Click here for capacitor for:
- Master P60 and P70, both Master 1.0 and 2.0
- Evolution P60 and P70
- V6 P70
-
Click here for capacitor for:
- Master P80, both Master 1.0 and 2.0
- Evolution P80 and P90
- V6 P90
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Click here for capacitor for:
