Fluctuating Pressure Sensor?
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Junior Member
Joined: Apr 2014
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2014 C250 Sport
Fluctuating Pressure Sensor?
Hi guys,
I have a 2014 C250 Sport (leased this April) and I'm wondering if anyone has had an issue with the pressure sensors lighting up "yellow" on the screen behind the steering wheel. I had my drivers side wheel light up yellow, then shortly after 2 of the rear wheels turned yellow. I might have pressed "up" or "left" on the wheel button and it seems like i reset the system and the wheels on the screen no longer are yellow. However, my PSI has dropped 2-3 since last night, and one of my wheels on the sensor continues to fluctuate up and down 1 psi while im driving. Is this normal? I think when I got out of my car this morning my front PSI's were at 30, and my back wheels were at 37.
I have a 2014 C250 Sport (leased this April) and I'm wondering if anyone has had an issue with the pressure sensors lighting up "yellow" on the screen behind the steering wheel. I had my drivers side wheel light up yellow, then shortly after 2 of the rear wheels turned yellow. I might have pressed "up" or "left" on the wheel button and it seems like i reset the system and the wheels on the screen no longer are yellow. However, my PSI has dropped 2-3 since last night, and one of my wheels on the sensor continues to fluctuate up and down 1 psi while im driving. Is this normal? I think when I got out of my car this morning my front PSI's were at 30, and my back wheels were at 37.
Super Member
Joined: Jan 2009
Posts: 929
Likes: 51
From: Silicon Valley, California
Factory ordered 2012 MB C350 w/Dynamic Handling Package
It is "lighting up yellow" because your tire pressure is beyond the safety range it was originally set to (whatever that may be). To prevent any false alarms try this...Once you have the desired pressures set (when cold), reset the tire pressure sensors from the steering wheel console. Then from here, if it ever flashes yellow again, then your tire pressure is definitely too low.
The PSI fluctuation is normal. As your tires heat up, the air inside expands and the same is inverse when it sits over night. The IDEAL time to adjust pressure is when the tires are at it's coldest temperature throughout the day. (this is also why you have to check your tire pressures at least once a season, since 12am in summer is different temperature than 12am winter).
I have a C350 so my weight is slightly different, but mine set to 40 PSI front and 43 PSI rear. I generally set all my tires to the theoretical maximum speed the car will travel and cross reference that with the speed rating of the tire on that axle.
For example...an H-Rated tire may be able to go 130 mph....but to do so safely, you'll need to inflate the cold pressure by 5 from OEM specs; whereas a Y-Rated tire may be able to do that without a pressure increase.
The PSI fluctuation is normal. As your tires heat up, the air inside expands and the same is inverse when it sits over night. The IDEAL time to adjust pressure is when the tires are at it's coldest temperature throughout the day. (this is also why you have to check your tire pressures at least once a season, since 12am in summer is different temperature than 12am winter).
I have a C350 so my weight is slightly different, but mine set to 40 PSI front and 43 PSI rear. I generally set all my tires to the theoretical maximum speed the car will travel and cross reference that with the speed rating of the tire on that axle.
For example...an H-Rated tire may be able to go 130 mph....but to do so safely, you'll need to inflate the cold pressure by 5 from OEM specs; whereas a Y-Rated tire may be able to do that without a pressure increase.
Super Member
Joined: Jan 2009
Posts: 929
Likes: 51
From: Silicon Valley, California
Factory ordered 2012 MB C350 w/Dynamic Handling Package
For a good read and a chart to determine how much PSI to increase your tires in relative to your top speed...go here...
http://www.tirerack.com/tires/tirete....jsp?techid=73
Remember, the OEM recommendation for tire pressures is for "normal" driving only. Any speed greater than 100mph, (regardless where it is performed, example track) must be adjusted accordingly.
http://www.tirerack.com/tires/tirete....jsp?techid=73
Remember, the OEM recommendation for tire pressures is for "normal" driving only. Any speed greater than 100mph, (regardless where it is performed, example track) must be adjusted accordingly.
Last edited by edgalang; Jul 17, 2014 at 08:30 PM.
