Active Seal Encoders

You probably have cabinets and draws full of expensive tools. Today, I’m going to show you how to use a cheap, but very effective, tool to check the orientation of the sensor encoder in a wheel bearing. ABS and other vehicle systems rely on information from sensors in the wheel bearings. In some bearings, that information comes from a magnetic sensor referred to as active seal encoders embedded in a seal. Inside the bearing, there is a toothed metal ring. As the wheel turns and the ring rotates near the seal, the sensor transmits that data to the vehicle, which uses it to calculate vehicle speed. Some generation one bearings use this technology. It’s a two row, pre-greased and sealed bearing assembly with the sensor in the seal.

If you install the bearing backwards with the seal encoder away from the sensor, the sensor will not be able to measure wheel speed. Once it’s installed incorrectly, you can’t just take the bearing out and reverse the orientation. When you remove it, you’ll destroy the seals and that means you have to buy a new bearing and you will have an unhappy customer when his or her bearing doesn’t work.

So, how do you make sure you orient a bearing correctly? If you have a magnetic encoder detector, place it against the side of the bearing. The magnets in the encoder will create a pattern in the detector. If you don’t have a detector, you can use any piece of lightweight magnetic metal, like a paperclip. Put the paperclip against the end of the bearing. If it sticks, you found a seal with the encoder. You can double check by putting the paperclip on the other end to make sure it doesn’t stick. When installing a bearing, press it in so that the seal encoder is next to the ABS sensor. So, if you work with sensored wheel bearings and want to avoid inserting them incorrectly, you may want to add a paperclip to your toolbox.