What Does a Pedal Potentiometer Do?

A potentiometer is an electrical position sensor. In Logitech G25, G27, G29, G920 and G923 pedals, it converts pedal movement into a changing electrical signal.

As you press or release a pedal, the potentiometer changes the signal voltage sent to the wheel. The wheel then converts this into the accelerator, brake or clutch position displayed by the PC or console.

Why Are Potentiometers Used?

Potentiometers are compact, simple and well suited to measuring pedal movement. Importantly, the Logitech wheel circuitry is specifically designed to work with potentiometers.

This is why the AXC SIM Potentiometer Upgrade Kit also uses potentiometers. It improves the physical design of the sensor while retaining the electrical operating principle that the Logitech electronics were designed to read.

Stock Logitech Potentiometers

The stock Logitech pedals use open rotary carbon-film potentiometers. Pedal movement is transferred to the potentiometer through a spring and a system of greased plastic gears.

Inside the potentiometer, a moving contact travels across a carbon track. Because the potentiometer is open, dust, dirt, hair and grime can reach its internal surfaces. Debris can also collect on the greased gears.

Contamination and wear can eventually cause symptoms such as:

• Flickering or jumping pedal readings
• An unstable pedal signal
• Dead spots during pedal movement
• Difficulty returning completely to 0%
• Difficulty reaching 100%

The original potentiometers are not generally available to purchase as replacement parts. They appear to have been made specifically for Logitech and are not a standard off-the-shelf component. Logitech does not normally supply them separately, making a direct like-for-like replacement difficult to obtain.

The stock arrangement is relatively indirect:

Pedal movement → spring and gears → rotary potentiometer → electrical signal

AXC SIM Upgraded Potentiometers

The AXC SIM Potentiometer Upgrade Kit uses a sealed linear membrane potentiometer, also known as a linear position sensor.

The potentiometer is mounted on a PCB fixed to the pedal chassis base. A nylon wiper attached to the moving pedal travels directly over the surface of the position sensor.

There are no gears or equivalent intermediate mechanisms:

Pedal movement → nylon wiper/linear position sensor → electrical signal

This provides a simpler and more direct connection between the pedal movement and its electrical output.

Because the position sensor is sealed, dust, dirt, grime and hair cannot reach its working surfaces, so external contamination does not affect its operation. It retains the potentiometer-based electrical output required by the Logitech wheel while providing many years of reliable use.

AXC SIM replacement potentiometers are supplied with a three-year warranty.

Stock vs AXC SIM Potentiometers

The AXC SIM Potentiometer Upgrade Kit replaces the unavailable and vulnerable open carbon-film sensor and geared mechanism with a sealed, direct-acting position sensor—without changing the electrical principle that the Logitech wheel was designed to use.

How to Test a Pedal Potentiometer with a Multimeter

A potentiometer can be tested by measuring the DC voltage between its signal connection and ground while the pedals are connected to a powered wheel.

Place the black multimeter probe on the potentiometer’s black ground connection and the red probe on its signal connection. Slowly move the pedal through its full travel. The signal voltage should change smoothly, falling as the pedal is pressed and rising as it is released.

Sudden jumps, dropouts or unstable readings at particular points in the pedal travel can indicate a contaminated or worn potentiometer. If the voltage changes smoothly at the potentiometer but the pedal output remains faulty, the problem may be in the wiring loom instead.

Take care not to short adjacent connections with the probes. Do not use the multimeter’s resistance setting while the pedals are powered.