TPMS: working or not?

<div class='quotetop'>QUOTE(dulcimer @ Nov 21 2007, 11:34 AM) [snapback]542431[/snapback]</div>

How far or how long have you driven the car since changing the tires?

I don't know the technical specifics of how the TPMS system works, but I can tell you from experience that when I put my winter tires on - mounted on a set of steel rims without TPMS sensors - I drive about 45 minutes to an hour in the morning before the light starts flashing. So it may still light up...

From my experience last winter running a second set of rims, most mornings the light is off when I leave my house, as I park the car in the garage overnight near the stacked wheels with the TPMS sensors. I have a long commute, so by the time I am getting close to work the light starts flashing. When I leave in the evening, the light flashes immediately upon startup. It generally repeats like this daily. However, toward the end of the winter, the TPMS light began to flash each time I started the car, at home or not. I remember hearing the TPMS sensors are powered by centrifugal force (?), so perhaps a few months of non-use wore down the batteries...? In any case, once I put them back on this summer and started driving, the light went off again (though I don't recall if it was immediate) and all was well with the world again.

 

I switched to my winter tires without TPMS sensors 5 days ago and the warning light has yet to come on in my car.

 

<div class='quotetop'>QUOTE(craigk @ Nov 26 2007, 01:30 PM) [snapback]544254[/snapback]</div>

My brother-in-law also switches to snow tires without TPMS, but his warning light comes on immediately and stays on all winter until he changes back to the standard tires with TPMS. His Prius is an 06. Maybe a change was made to the 07, but I doubt it. I recommend that the dealer check to see why your warning light is not on.

 

<div class='quotetop'>QUOTE(craigk @ Nov 26 2007, 11:30 AM) [snapback]544254[/snapback]</div>

Where do you store your summer wheels? There have been a few posts that talked about the range of the TPMS signal and storing summer wheels in the same garage as your Prius, which makes it see the sensors. Of course, eventually you will drive away for long enough to get the system to complain.

Tom

 

She said she had the snow tires put on the original wheels WITH the TPMS sensors. So if the sensors are on the car the light will not come on unless the pressure is too low.

The way the sensor would be "damaged" is the goop would plug the sensor element. The only way to test for this would be to lower the pressure in that tire at least 25% below the other tires, or what the pressure was when you last set the sensors (button below steering wheel has to be held in for a few seconds until the light flashes at you to set the "standard pressure").

If you want to test the sensor, inflate all the tires to, say, 42 PSI front and 40 PSI rear (make sure the tire rating on the sidewall is ok with this pressure - it will list "maximum pressure at maximum load=XX"). Then hold in the button. Once set, then lower the pressure in the suspect sensor wheel by 30% - say to 28 PSI. Turn on the car, but don't drive at high speeds - in fact you shouldn't have to drive at all. If the light comes on the sensor is fine. If it doesn't it may need more testing, or you may have to wait longer. When you are done be sure to re-inflate the test wheel back to your standard pressure.

Even if the sensor is damaged it's not a big deal. Yes, it could be considered a "safety issue", just like all cars made until about three years ago which didn't have the TPMS system. So it's your choice if you want to spend the $150 or so to have it replaced and the system re-paired with the sensors (the system will not recognize the new sensor until it is re-paired).

 

<div class='quotetop'>QUOTE(qbee42 @ Nov 26 2007, 12:46 PM) [snapback]544262[/snapback]</div>

My summer tires with TPMS are in the garage about 10' from the car and 8' up in the air. My car has been away from the garage for hours with no warning yet. I don't mind, I won't get it checked out. I check my tires often enough and would rather not have to use the "Cartalk" method (black tape) to cover the warning light all winter.

 

<div class='quotetop'>QUOTE(craigk @ Nov 26 2007, 12:57 PM) [snapback]544302[/snapback]</div>

My memory on this topic is a bit sketchy, but I seem to recall that it takes more than a few hours before the system complains. If the pressure drops while a sensor is still in range, then you get a warning right away, but I believe it takes a while before the TPMS system will complain about the loss of a sensor.

Anyone want to refresh my memory?

Edit: Here is a link to one of the TPMS posts: Link

Tom

 

I thought the sensor in the tire had to actually *move* a bit before
it would start transmitting?? Thus tires stored in the garage
wouldn't talk to the car? Or is there some other trigger?
.
_H*

 

<div class='quotetop'>QUOTE(qbee42 @ Nov 26 2007, 07:04 PM) [snapback]544417[/snapback]</div>

Thanks for the link!

 

<div class='quotetop'>QUOTE(hobbit @ Nov 26 2007, 07:56 PM) [snapback]544474[/snapback]</div>

Good question. I assumed the sensors were polled by the car. That could be gated by requiring the car to move, or just be powered on, but I have no real data. Anyone know for sure?

Tom