I have let some pressure out of one of the tyres to see if I got a warning light on the clocks but nothing happened.
Thanks in advance
![Image](http://i52.tinypic.com/4j2kpd.jpg)
Norbreck21a wrote:Actually it works using the ABS sensor to measure rolling radius. When you press the "SET" button and get a beep, the system resets itself, and the ABS module monitors each wheel and "measures" the full rotation of each wheel using the ABS sensor.
When one tyre is flat or going down, the rolling radius of the tyre increases as the "flat spot" on the tyre gets bigger. Therefore the ABS sensors are monitoring the wheels, and suddently one says, "hang on, I was supposed to get a signal just then but it was xx milliseconds late, I must have a flat tyre", and it illuminates the symbol on the dash and within the highline screen (if fitted).
As it runs on rolling radius, it does take a fair amount for the sensors to detect a tyre going down, as it isn't actually measuring the pressure inside the tyre. It's not foolproof and it's a cheap system, but I'd rather have it than nothing. Escpecially with most cars running expensive alloys these days.
i think you just answered my question - tyre warning light came on after i changed wheels on the weekendGrey_Polo wrote:If you have the tyre pressure warning the switch is not the blank one you show. It is located in the glove box next to the air bag on/off switch and has a tyre drawing on it.
You are supposed to press this switch after checking the air pressure or changing the wheels. This resets the calibration...