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Hey All,

I live in California and got my A5 back in August when it was still 90+ degrees...Now that we've had a significant drop in temperature, the mornings are chilly and the "tire pressure alert" came on the other day. I filled up the tires with air to the proper PSI and the alert remained on until I told the car through the MMI setup that this was in fact the proper pressure...

This is the second time this has happened (took it to the dealer before, he did the same thing...), and I was wondering if I will have to "override" the setup options every time to tell the car it's at the proper PSI? Isn't the car alert supposed to go off as soon as I fill them with air and it reaches the noted pressure? Anyone have this problem? Thanks in advance!
 

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Isn't the car alert supposed to go off as soon as I fill them with air and it reaches the noted pressure? Anyone have this problem?
Yeah, the same thing happened with me about a week or so ago when we had cooloer temperatures overnight. Like you, I figured the TPMS warning light would go off by itself after I added more air to the tires, but that didn't happen. I too ended up having to "override" the previously stored PSI. :confused:
 

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Try using nitrogen

Read
 

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I'm not sure, would have to do some research, or something drastic like 'read the manual (RTFM) ! ...but I think TPMS systems are 'relative' and do not obtain 'absolute' values.

In other words they measure changes in pressure not the actual pressure value. I believe they are triggered when one or several tyres hit a threshold in pressure change (a few PSI I guess). Therefore, I would expect you to have to prompt the system ech time a presure correction is made because it has no idea that you have just topped tham up correctly, just that there's been another change beyond the threshold... and hence the warning light coming on again after the correct pressures were restored.

...I'm guessing again, but I don't think they retain a memory of the sensor reading at the time of 'reset' but retain a buffer of data equivalent to a suitable duration, e.g a few hours/days. Therefore, as systems designed to alert more 'rapid' deflations and designed initially for run-flat tyres so the driver would know they had a puncture, I imagine it could be possible for all 4 tyres to deflate very slowly over many months and not trigger the system if the deflation were even... possibly, maybe!!!

Prof.
;)
 
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