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-   -   Tire pressure light not on!! (http://www.focusfanatics.com/forum/showthread.php?t=305111)

jeff_nc 12-27-2012 02:29 PM

Tire pressure light not on!!
 
Just put winter tires and steel wheels on my Focus. The tire dealer installed valve stems that would work with sensors, but not the sensors themselves. I was expecting the warning light to come on, but, nada, zilch, zip.

The light comes on when I start the car, then goes out just like it did before. Any ideas?

PratoN 12-27-2012 02:52 PM

Quote:

Originally Posted by jeff_nc (Post 4514230)
Just put winter tires and steel wheels on my Focus. The tire dealer installed valve stems that would work with sensors, but not the sensors themselves. I was expecting the warning light to come on, but, nada, zilch, zip.

The light comes on when I start the car, then goes out just like it did before. Any ideas?

You've got to drive 20 miles or so before it starts yelling at you every start-up. Also, if you park near your tires, you'll also have some interesting experiences.

I put my winter tires on a month ago and whenever I drive to my parents house (where my summer tires are) I'll go from a pressure monitor "fault" to "low tire pressure" (one of my summer tires had a nail in it near the edge and I'm stalling on getting that fixed.) Strange that it still sends out that signal after being inactive for so long. Hmm - I wonder if that's killing the battery...

WhiteTite 12-27-2012 09:02 PM

When I had my Mustang, I had aftermarket wheels on it with no sensors, but I had the stock tires and wheels in the garage. The TPM never came on, unless I was 40 miles from home. Come back into the garage light would go out and not come on as long as I was not traveling out of the area. Strange, I know....

Deftmetal 12-27-2012 09:10 PM

The sensors are passive and the car doesn't need a signal saying all is well

suss6052 12-27-2012 09:15 PM

Quote:

Originally Posted by Deftmetal (Post 4514721)
The sensors are passive and the car doesn't need a signal saying all is well

The sensors are not passive. Why do people keep saying this? They need to detect movement in order to function properly, therefore how can they be considered passive?

Deftmetal 12-27-2012 09:19 PM

It makes sense to me. I don't choose to believe so many people have sensors that don't work. Like you said I've read it a lot

suss6052 12-27-2012 09:32 PM

Per the owners guide:
Quote:

Understanding your tire pressure monitoring system (TPMS)
The tire pressure monitoring system measures pressure in your four road
tires and sends the tire pressure readings to your vehicle. The low tire
pressure warning light will turn on if the tire pressure is significantly low.
Once the light is illuminated, your tires are under-inflated and need to be
inflated to the manufacturer’s recommended tire pressure. Even if the light
turns on and a short time later turns off, your tire pressure still needs to
be checked
Pg 246 of version 5.

The car uses direct pressure sensors mounted inside the tire (at the valve stem) not an indirect or imprecise measuring system.

Quote:

Direct Monitoring Systems

Direct tire pressure monitoring systems measure, identify and warn the driver of low pressure. Because direct systems have a sensor in each wheel, they generate accurate warnings and can alert the driver instantly if the pressure in any one tire falls below a predetermined level due to rapid air loss caused by a puncture. In addition, direct tire pressure monitoring systems can detect gradual air loss over time. Some direct systems use dashboard displays that provide the ability to check current tire pressures from the driver's seat.

Direct systems attach a pressure sensor/transmitter to the vehicle's wheel inside the tire's air chamber. Most Original Equipment and some aftermarket systems attach their air pressure sensor/transmitter to special tire valves. While the presence of a metal clamp-in valve typically identifies the presence of a direct tire pressure monitoring system, special snap-in rubber valves have also been used to support direct system sensors. The transmitter's signal is broadcast to the in-car receiver and the information is displayed to the driver.
http://www.tirerack.com/tires/tirete...jsp?techid=44&

Quote:

Tire Pressure Monitoring System (TPMS) - Overview
Overview

The BCM monitors the tire pressure in the 4 road tires with tire pressure sensors that communicate the tire pressure via radio signals to the BCM. The tire pressure sensors are battery operated and mounted to the valve stems. All of the controlling software for the TPMS is contained in the BCM. The IPC illuminates the TPMS warning indicator and the message center displays a message when a fault is present or when the tire pressure falls below the low pressure limit.
Quote:

TPMS Sensor

Each of the 4 TPMS tire pressure sensors contain a battery, a tire pressure sensor and a radio transmitter. The TPMS sensor radio transmissions are sent approximately once every 60 seconds when the vehicle speed exceeds 32.2 km/h (20 mph).
This last quote from the factory service manual states that the sensors send off signals once every 60 seconds above 20 mph.

jeff_nc 12-28-2012 11:53 AM

Thanks for this info, suss6052. I understand the system a lot better now.

So the question is, do I need to take the car in to have the system checked? I have driven the car about 40 miles on the new wheels and still no light.

Vernl 12-28-2012 12:22 PM

Quote:

Originally Posted by jeff_nc (Post 4514230)
Just put winter tires and steel wheels on my Focus. The tire dealer installed valve stems that would work with sensors, but not the sensors themselves. I was expecting the warning light to come on, but, nada, zilch, zip.

The light comes on when I start the car, then goes out just like it did before. Any ideas?

Im not sure I understand your post....your valve stems are the sensor ..or they aren't... you cant install the sensors into the valve stems at a later date becasue the stem itself has it built in.Sounds to me like they installed proper valvestem/sensor already

jeff_nc 12-28-2012 12:40 PM

Quote:

Originally Posted by Vernl (Post 4515513)
Im not sure I understand your post....your valve stems are the sensor ..or they aren't... you cant install the sensors into the valve stems at a later date becasue the stem itself has it built in.Sounds to me like they installed proper valvestem/sensor already

No, they only installed valve stems that could accept sensors at a later date. The stems were $4 each, the sensors were like $40 each, so I passed. If I got sensors for $4 I would be REALLY happy!


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