my fan turns on but only works on the lowest speed setting, the higher speeds do nothing.

Diagnosis

The Rowenta VU5670 Turbo Silence Stand Fan utilizes a multi-stage electronic speed control system. When the fan operates exclusively on the lowest speed setting and ignores inputs for medium or high, the root cause is typically a failure in the switching circuit on the main printed circuit board (PCB) located in the base. Specifically, the triacs or capacitors responsible for modulating the voltage to the motor have failed. In this model, the low speed often bypasses certain control stages or uses a different capacitor path, which is why it remains functional while the higher-draw settings fail.

This failure is often caused by voltage spikes or overheating of the control components during prolonged high-speed operation. To confirm this, you can perform a "button continuity test" if you have a multimeter. If the buttons register a press but the motor doesn't ramp up, the issue is not the physical switch but the power-delivery components on the board. Look for a "burnt" smell emanating from the base or a slight discoloration (browning) on the green PCB surface near the power input area.

How to Fix It

To resolve this, you must access the internal control board and perform a component-level repair or replace the PCB. Follow these steps precisely:

1. Power Isolation: Unplug the fan from the wall outlet. Do not attempt this while the unit is connected to power, as the capacitors on the board can hold a lethal charge.
2. Base Disassembly: Turn the fan upside down. Remove the four Phillips head screws securing the bottom plastic plate of the base. Carefully lift the plate to reveal the main PCB and the wiring harness.
3. Visual Inspection: Examine the board for "bulging" electrolytic capacitors (the tops should be flat, not domed). Look for scorched areas around the triacs—these are the small three-legged components that handle the high-current switching.
4. Solder Joint Refresh: Use a soldering iron to reflow any "cold" or cracked solder joints, particularly where the main power cord enters the board and where the motor wires connect. Cracked joints often cause high-resistance paths that prevent the motor from reaching high speeds.
5. Component Replacement: If a capacitor is bulging, identify its rating (e.g., 10uF 25V) and replace it with an identical specification part. If a triac is burnt, it must be desoldered and replaced with a compatible semiconductor.
6. Testing: Before closing the base, ensure all wires are tucked away from the edges of the plastic housing to prevent pinching. Reassemble the base and test the speed cycles.

If That Didn't Work

• Motor Capacitor Replacement: The VU5670 relies on a start/run capacitor located near the motor housing. If this capacitor has degraded, the motor may have enough torque to spin at low speed but lack the electrical "push" to accelerate to higher RPMs. Replace the motor capacitor with a new one matching the exact microfarad (uF) rating.
• Control Panel Ribbon Cable: Check the thin ribbon cable connecting the buttons to the main PCB. If the cable is pinched or has a hairline fracture, the signals for "Medium" and "High" may not be reaching the controller. Clean the contacts with 90% isopropyl alcohol and reseat the connector.
• Motor Bearing Friction: If the bearings are seized or dry, the motor may be physically unable to reach higher speeds due to mechanical resistance. Spin the blades by hand; if they feel stiff or "gritty," apply a drop of high-grade synthetic machine oil to the motor shaft.
• Full PCB Replacement: If multiple components on the board are scorched, a board-level repair is impractical. Source a replacement VU5670 control board and swap the entire unit, ensuring the wiring harness is seated firmly.

Heads Up

• Voltage Warning: Always discharge the capacitors using a resistor before touching the PCB to avoid electrical shock.
• Avoid Overloading: Do not run the fan on the "Turbo" setting for more than 12 consecutive hours, as this puts maximum stress on the control triacs.
• Dust Maintenance: Every 3 months, use compressed air to blow out the motor vents in the rear of the fan head. Dust buildup causes the motor to run hotter, which degrades the electronic components in the base.
• Power Surge Protection: Plug your Rowenta fan into a high-quality surge protector. The electronic speed controllers in these models are highly sensitive to grid fluctuations.