Service Tire Monitor.Light

[DrJ]

Just had new tires put on and they put new parts in so the stem wouldn't fail.They said light could be caused by failing battery pack inside rim.Estimate to replace was about $250/per tire to replace. Does this seem right? I declined but now light comes on and off all the time. ANY way to disconnect the warning light? DrJ.....

[fishing tech]

What kind of vehicle? If you had some rookie do the job they may have broke the sensor during removal or install of the tire.

[Macgyver55]

Depending on the vehicle, tire pressure sensors are around 60 bucks retail and you can get them for even less on the bidding sites.

I can't think of any that are anywhere near that expensive, (250 each?) and they can be replaced in minutes so labor should be minimal.

Also depending on the vehicle you can often program them yourself.

[luckycrank]

Make sure your tires are filled to the cars recommended air pressure . Not all shops tire gauges are calibrated .. tire pressure drops 1 p.s.i for every 6 deg in temperature.

so say the thresh for the monitoring system is 29 - 40 p.s.i

If they put tires on your car one afternoon @ 80 degrees inflated them to 32 p.s.i ( +/- 1deg. Do To inproperly calibrated tire gauge . ) the next morning the air temp is now 65 deg. (15 deg. Diff) the air pressure in you tires is now 30 p.s.i. +/- 1deg. Dangerously close to the low pressure thresh hold of your low tire alert.

It could be a bad battery it is a legit cause ? But odd it wasnt presnt just hours before you put tires on .. or they may have stressed.a sensor . Or improperly retrained the tire position after tire swap.

[luckycrank]

F.y.i nitrogen does not expand and contract with temperature as long as you dont mix it air . And rectifies alot of tire pressure sensor issues just a thought

[delcecchi]

F.y.i nitrogen does not expand and contract with temperature as long as you dont mix it air . And rectifies alot of tire pressure sensor issues just a thought

I hate to get involved in that but nitrogen does change pressure with temperature just like air and argon and any other gas.

And since 70 degrees is 530 above absolute zero, to change a 30 psi tire by 1 psi out of 44 psi absolute pressure would be 2.2 percent of 530 or about 12 degrees.

[Jeremy airjer W]

And since 70 degrees is 530 above absolute zero, to change a 30 psi tire by 1 psi out of 44 psi absolute pressure would be 2.2 percent of 530 or about 12 degrees.

Uh, what?

From what I see in the shop 1 psi for every 10 degrees of temperature change is pretty close to being accurate from temps in the 50 to 80 range. 50 to freezing it is less dramatic, and after freezing it really doesn't make any difference in tire pressure.

Back to the question. It is entirely possible that the new tires in combination with older TPM sensors with batteries that a getting low are the problem. I am seeing this more and more as TPMS systems are starting to near there sensor battery life spans.

I also agree that the tires need to be set to the tire pressure displayed on the tire pressure placard on the vehicle NOT to the spec listed on the tire. Some of the newer TPMS systems will also turn on the light for overinflated tires.

[DrJ]

I had the tires replaced at Discount Tires. The light came on and off before new tires. It will come on and 1 tire pressure will be read blank and then the next day no light and all 4 show correct tire pressure. They said since it was intermitent that it was probably the battery failing. It's a 2005 Tahoe. Is the battery pack inside the rim so all the tires would need to come off and be remounted? Thanks DrJ...

[Jeremy airjer W]

If it's only one sensor than start with that one...

[delcecchi]

Uh, what?

From what I see in the shop 1 psi for every 10 degrees of temperature change is pretty close to being accurate from temps in the 50 to 80 range. 50 to freezing it is less dramatic, and after freezing it really doesn't make any difference in tire pressure.

Back to the question. It is entirely possible that the new tires in combination with older TPM sensors with batteries that a getting low are the problem. I am seeing this more and more as TPMS systems are starting to near there sensor battery life spans.

I also agree that the tires need to be set to the tire pressure displayed on the tire pressure placard on the vehicle NOT to the spec listed on the tire. Some of the newer TPMS systems will also turn on the light for overinflated tires.

The original guy said 1 psi for 6 degrees, which seemed high to me. (and said that nitrogen doesn't change. Ho ho) My doing the math in my head said 12 degrees per psi. I would believe 10. Not 6.

Good old ideal gas law PV/T=Constant. (T is temperature above absolute zero)

Your Geek Friend,

[Jeremy airjer W]

The original guy said 1 psi for 6 degrees, which seemed high to me. (and said that nitrogen doesn't change. Ho ho) My doing the math in my head said 12 degrees per psi. I would believe 10. Not 6.

Good old ideal gas law PV/T=Constant. (T is temperature above absolute zero)

Your Geek Friend,

I missed the 6 degree part....

[Capt. H (Ret.)]

$250 per tire???!!!! That's nuts. I doubt there is any way to disconnect the warning light because even if you don't install the STM it will probably light up because it is not receiving a signal. I'd shop around.

Mike