Dear Car Talk:
Do tire pressure sensors use individual batteries (that may last only 10 years) rather than the car's electrical system? Could such a battery replacement cost about $85 for each wheel? What about other sensors on the car? Are they battery powered, too? -- Ken
Let me guess, Ken. You just had to replace a tire pressure sensor, and it cost you $85?
Yes, each tire pressure sensor uses its own battery. They tried hard-wiring them, but the car only got about 10 feet down the road before the wires got hopelessly wrapped around the car's axles. So, battery power was really the only practical way to go for a sensor that lives inside a tire.
Most of them last about 7-10 years -- less if you do a lot of stop-and-go driving, because the sensors only send their signals to the car's computer when the car is stopped. When the battery finally does die, it can be replaced. But since most of the labor involves removing the tire from the wheel, it's silly to not just replace the whole sensor, which comes with a new battery. And $85 is about the right price for the job.
You'd be miffed if you paid to have the sensor removed and the battery replaced, then have a 10-year-old sensor fail a few months later due to an age-related problem. So, we always replace the whole sensor.
We also use only original equipment sensors from the manufacturer. You can get cheaper, aftermarket sensors that claim to work on different cars. But in our experience, they sometimes have trouble communicating with the car's computer. And then you've got the same problem: You've spent $50, and then you've got to spend $85 and start all over again.
The tire pressure sensors are the only sensors that are powered by their own batteries, Ken. Pretty much everything else on the car can be wired directly. It's just the unique setting of the tire pressure sensor -- spinning inside a sealed tire -- that calls for a battery powered solution.
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