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All AVA Master and Evolution models (P40–P90) use single-phase induction motors – a durable and efficient motor type well suited for high-performance pressure washers. This guide explains how the motor circuit works, common symptoms of failure, and how to test and replace key components like windings, capacitors, and switches.
What is an Induction Motor?
An induction motor relies on magnetic fields to turn the rotor (motor shaft). Unlike brushed motors, there are no wearable parts like brushes or commutators – making them more reliable and quiet.
A typical AVA induction motor system includes:
- Stator with two windings: main (run) and auxiliary (start).
- Start capacitor (e.g. 35 µF) for startup torque.
- Motor housing (metal) connected to ground.
- Micro switch that controls motor activation via water pressure.
- Main switch for user control.
- Earth cable for safety.
Electrical Circuit Overview
The AVA induction motor system includes the following components:
| Component | Function |
|---|---|
| Power cord | Brings live, neutral, and earth into the machine |
| Main switch | Turns the power on/off |
| Capacitor | Temporarily boosts starting torque by energising auxiliary winding |
| Induction motor | Converts electrical energy into rotation |
| Micro switch | Activates motor based on water flow (TSS system) |
| Grounding system | Protects user from electric shock – must always be connected properly |
Always ensure the earth wire is reconnected to clean, bare metal when servicing the motor.
Typical Motor Symptoms and Possible Causes
| Symptom | Possible Cause |
|---|---|
| Humming but not starting | Faulty capacitor, stuck rotor, or low voltage |
| Starts only when manually turned | Weak or failing capacitor |
| No response at all | Defective switch, open circuit in windings |
| Tripped fuse / blown breaker | Shorted capacitor, pinched wires, faulty motor |
| Burning smell or overheating | Motor overload, capacitor fault, poor ventilation |
How to Test the Induction Motor
Tools Required:
- Multimeter with resistance (Ohm) and capacitance (µF) modes.
- Basic tools for disassembly.
- Safety gloves and eye protection.
1. Measure the Windings (Resistance Test)
All AVA motors have two cables from the motor:
- One with black outer sheath → Main (run) winding.
- One with white outer sheath → Auxiliary (start) winding.
Each cable has 2 conductors (black + white).
Do not mix wires from different cables when measuring.
| Step | Instructions |
|---|---|
| Disconnect capacitor | Prevents false readings |
| Measure main winding | Place multimeter probes on both wires inside black cable |
| Measure auxiliary winding | Place probes on both wires inside white cable |
| Acceptable readings (approx.) | See table below |
Reference Values (at 20 °C)
| Model | Main Winding | Auxiliary Winding |
|---|---|---|
| P60 | 5.73 Ω | 2.45 Ω |
| P70 | 4.75 Ω | 2.17 Ω |
| P80 | 2.40 Ω | 1.49 Ω |
A deviation of up to ±10% is acceptable.
If you measure ∞ (open) or 0 Ω (short) → the motor is defective.
2. Capacitor Test Without Capacitance Mode
If your multimeter doesn’t support µF measurement:
- Disconnect the capacitor.
- Set multimeter to Ohms (Ω).
- Place probes on the terminals.
- Look for a brief drop then rise in resistance (charging behaviour).
- Reverse the probes – same result expected.
| Result | Interpretation |
|---|---|
| Drops, then rises to ∞ | Capacitor is charging – good sign |
| Shows 0 Ω continuously | Short circuit – replace |
| Shows ∞ immediately, no change | Open circuit – replace |
For more accuracy, see our capacitor article.
3. Switches and Safety Tests
| Component | Test Type | Good Reading |
|---|---|---|
| Micro switch | Press = 0 Ω / Released = ∞ | Clean toggle |
| Main switch | ON = 0 Ω / OFF = ∞ | Smooth change |
| Power cord | End-to-end continuity | All lines conducting |
| Ground wire | Plug to motor = 0–1 Ω | Solid connection |
Replacement Recommendations
If one electrical component has failed, the stress may have damaged others.
To ensure reliable repair, AVA recommends replacing the complete preassembled switch box, which includes:
- Main switch.
- Micro switch.
- Start capacitor.
- Mounting base and screws.
Tips for Reassembly
- Reconnect the capacitor correctly (orientation matters).
- Ensure earth wire is screwed to clean metal.
- Route cables safely — avoid contact with moving parts or sharp edges.
- Never run the motor without a working capacitor.
Summary
| Test | Result | Action |
|---|---|---|
| Windings within range | ✅ | Motor OK |
| Capacitor charges/resets | ✅ | Capacitor likely OK |
| Switch toggles correctly | ✅ | No replacement needed |
| Resistance too high/low | ❌ | Replace affected component |
If you're in doubt, always consult a service guide or contact AVA Support.
Proper diagnostics will save time, parts, and frustration.
