Cadence Sensor Not Working?

Cadence sensors fail in a frustratingly uniform way: the number simply is not there. The useful thing is that the causes are a short, fixed list, and they have a natural order — cheapest and most likely first. Work down it.

1. It is asleep

Every current cadence sensor is magnet-less and sleeps between rides to protect the coin cell. It wakes on rotation, not on being asked politely by an app. Spin the cranks for five to ten seconds, keep pedaling, and then open the pairing screen.

If the sensor has an LED, it blinks while it is awake and broadcasting. That single light splits the problem in half: blinking means the sensor works and the issue is on the receiving end; nothing means the sensor is the problem.

2. The battery

A CR2032 does not fail cleanly. As it fades you get intermittent readings, cadence that drops to zero during hard efforts and recovers, or a sensor that pairs and then disappears ten minutes in. All of that looks like a software problem and is not.

Garmin claims up to about twelve months for its Cadence Sensor 2; Wahoo quotes around 200 hours for the TRACKR Speed. If you cannot remember changing it, change it. Note the orientation of the old cell, and make sure the rubber gasket seats properly when you close the case — a bad seal is how sweat gets in, which is a real risk on a trainer bike.

On a brand-new sensor, check for the plastic battery tab. It is still the single most common cause of a sensor that has never worked.

3. It is paired somewhere you forgot about

This is the one that wastes the most time. If you bonded the sensor in your phone's or tablet's system Bluetooth settings, the operating system may hold the connection and the app will never see it. Most cycling apps want to connect to the sensor directly.

The fix: go into system Bluetooth, forget the device, then pair it inside Zwift or your training app. The same applies if another app or a second head unit nearby is holding the sensor — Bluetooth sensors generally only talk to one receiver at a time.

4. You have run out of Bluetooth connections

Apple TV allows two simultaneous Bluetooth connections, and a trainer plus a heart rate strap uses both. Add a cadence sensor and something has to go. This is not a fault, it is a documented platform limit, and it is covered in Zwift on Apple TV.

There are three ways out: drop a sensor you do not need, use the Zwift Companion app as a bridge for some devices, or move to ANT+, which has no practical connection limit. On a PC or Mac an ANT+ dongle on an extension cable solves this and several other problems at once.

5. The sensor is in the wrong mode

Dual-purpose sensors such as the Magene S3+ and the Coospo do one job at a time: speed orcadence. A sensor set to speed mode and banded to a crank arm will pair happily and report nothing useful, which reads as "not working" even though everything is functioning.

Check the mode, set it deliberately, and confirm you are selecting the Cadencebox in your app's pairing screen rather than the speed one.

6. It has moved on the crank

Rubber bands relax. A sensor that can rotate on the arm reads intermittently, exactly like a failing battery. Twist it with a finger: if it moves, re-band it tight, and check it clears the chainstay through a full backwards revolution.

If the crank shape simply will not hold a band — deep aero profiles, oversized arms, an arm with a power meter already bonded to it — move the sensor to a shoe clip if yours supports one. How to install a cadence sensor covers the mounting options properly.

The short answer

If the sensor really is dead

#	Product	Best for	Score	Price
1	Garmin Cadence Sensor 2 The replacement to buy if the dead sensor was a Garmin, and the one whose claimed year-long battery makes this fix list come up least often.	Best replacement for a Garmin setup	8.7★★★★☆8.7 out of 10	$64.11 · View on Amazon $69.99Save 8% #ad We may earn a commission · Price as of October 21, 2026
2	Magene S3+ The pragmatic buy when you are not sure whether the sensor or the setup is at fault: cheap, dual-band, and it covers both sensor jobs.	Cheapest way to rule out a faulty sensor	8.5★★★★☆8.5 out of 10	$16.99 · View on Amazon #ad We may earn a commission · Price as of October 21, 2026
3	CYCPLUS ANT+ USB Receiver Stick The fix when the sensor is fine and Bluetooth is not: an ANT+ dongle on an extension cable solves dropouts that no amount of re-pairing will.	The fix when Bluetooth is the problem	8.5★★★★☆8.5 out of 10	$16.99 · View on Amazon #ad We may earn a commission · Price as of October 21, 2026

When the answer is that you do not need it

Before you replace anything, check whether your trainer already reports cadence. Most current smart trainers do, and if yours is one of them the sensor is duplicating data you already have — and consuming a Bluetooth connection to do it.

On Zwift specifically, cadence is displayed rather than used: the simulation derives your speed from power, weight, gradient and draft. Do you need a cadence sensor for Zwift makes that case in full, and what cadence should you ride at covers what to do with the number once you have it.

And if the thing that is actually dropping out is the trainer rather than the sensor, smart trainer not connecting to Zwift is the right list to work through instead.