Not so easy this time - Low tire pressure indicator

53tin · 04-01-2009, 08:56 PM

My 2001 Windstar has a system to monitor for low tire pressure. I think it uses the wheel speed sensors to detect a difference in wheel speed when a tire gets low (Just guessing, but I don't see how else it could work.)

Anyway the switch to turn it on and off is right above the traction control switch near the center of the dashboard. The switch has an amber LED to let you know when it is off.

A couple of months ago I noticed that it was turned off. I turned it back on but when I put the van in reverse the low tire pressure system is turned off again. If I go directly from Park to Drive it stays on.

One other thing I noticed is that when I go to reverse and it is turned off I have to hit the switch twice to turn it back on. After that I can toggle it on and off by hitting the switch once.

Any ideas where to start on this one?

53tin

LastTudor · 04-01-2009, 08:59 PM

Quote:

Originally Posted by 53tin

My 2001 Windstar has a system to monitor for low tire pressure. I think it uses the wheel speed sensors to detect a difference in wheel speed when a tire gets low (Just guessing, but I don't see how else it could work.)

Anyway the switch to turn it on and off is right above the traction control switch near the center of the dashboard. The switch has an amber LED to let you know when it is off.

A couple of months ago I noticed that it was turned off. I turned it back on but when I put the van in reverse the low tire pressure system is turned off again. If I go directly from Park to Drive it stays on.

One other thing I noticed is that when I go to reverse and it is turned off I have to hit the switch twice to turn it back on. After that I can toggle it on and off by hitting the switch once.

Any ideas where to start on this one?

53tin

I'm almost positive the system uses sensors in the wheels inside the tires themselves that sense pressure and send a wireless signal back to a receiver. At the age of your Windstar, I'd wonder if maybe one or more of the sensor's batteries were getting weak. That might make it act flaky

53tin · 04-01-2009, 09:12 PM

That's pretty cool then. I can see how a low battery could cause it to give false info about a tire being low- there's a light on the dash that lights up to tell you that one of the tires is low. Do you think that a bad battery causing one of the tires to report low pressure would cause it to turn off the whole system when going to reverse? And then there's that other little thing about having to hit the switch twice to turn it back on.

If the sensors are inside the tires then I guess I'd have to dismount the tires to change the battery, huh? I guess I'd have to change all four to be sure. Any idea where to find out what batteries they use?

Thanks for the info.

53tin

LastTudor · 04-01-2009, 09:20 PM

Quote:

Originally Posted by 53tin

That's pretty cool then. I can see how a low battery could cause it to give false info about a tire being low- there's a light on the dash that lights up to tell you that one of the tires is low. Do you think that a bad battery causing one of the tires to report low pressure would cause it to turn off the whole system when going to reverse? And then there's that other little thing about having to hit the switch twice to turn it back on.

If the sensors are inside the tires then I guess I'd have to dismount the tires to change the battery, huh? I guess I'd have to change all four to be sure. Any idea where to find out what batteries they use?

Thanks for the info.

53tin

I have a friend who's a manager at a Sears Auto Center. I know that they deal with those every day. My recommendation, since the tires have to be broken down anyway, is to find a shop that does tires. They'll know exactly what your sensors need.

theoldwizard · 04-02-2009, 12:47 AM

Quote:

Originally Posted by LastTudor

I'm almost positive the system uses sensors in the wheels inside the tires themselves that sense pressure and send a wireless signal back to a receiver.

Sorry, the old ones uses wheel revolutions per mile. Not very accurate because they would completely miss 4 tire that were too low or too high by equal amounts. The system was "free" (a few software changes in the ABS module) except for the light bulb.

I had a friend who had this system on a Windstar. When she replaced the tires (at the dealer) the light would come on within less than 20 miles. They basically told her to put a piece of tape over the bulb, because they did not know how to fix it.

LastTudor · 04-02-2009, 01:52 AM

Quote:

Originally Posted by theoldwizard

Sorry, the old ones uses wheel revolutions per mile. Not very accurate because they would completely miss 4 tire that were too low or too high by equal amounts. The system was "free" (a few software changes in the ABS module) except for the light bulb.

I had a friend who had this system on a Windstar. When she replaced the tires (at the dealer) the light would come on within less than 20 miles. They basically told her to put a piece of tape over the bulb, because they did not know how to fix it.

Thanks for filling me in. I know the newer systems use sensors in the wheels 180 degrees away from the valvestems. I didn't know that there was an old system that counted. It sounds like it works in conjunction with the ABS system then, using the tone wheel to count revolutions.

Do you know when they made the switch to the more sophisticated system?

53tin · 04-02-2009, 05:03 AM

But still, It doesn't seem to be a problem with false indications, it's a problem with it being turned off every time that I put it in reverse. This behavior started a couple of months ago so I know that it isn't by design. It's also weird that I have to hit the switch twice to turn it off.

GraybeardAv · 04-02-2009, 05:20 AM

Have you read the owner's manual? Like they say, "RTFM, Read the Manual."

IIRC, you have to hold the button a few seconds to reset the monitor. That way it will compensate for different size tires.

GB

53tin · 04-02-2009, 08:44 AM

Yes, I RTFM and I even understood it. The tire pressure reset is located to the left of the steering column on the dash. It recalibrates the system if it displays a low tire pressure indication on the instrument panel.

I'm not talking about the low tire pressure indicator on the instrument panel. The amber LED that I'm talking about is on the center of the dash just above the traction control on/off switch. It is a simple on/off toggle that turns the system on and off.

Once again, the symptoms are the LED illuminates when I put the van in reverse; which indicates that the Tire Pressure System is turned off- not that I have low tire pressure. It doesn't do it when I go directly into drive. To re-enable it I have to press the on/off button twice.

philkb · 04-02-2009, 06:15 PM

Quote:

Originally Posted by 53tin

Yes, I RTFM and I even understood it. The tire pressure reset is located to the left of the steering column on the dash. It recalibrates the system if it displays a low tire pressure indication on the instrument panel.

I'm not talking about the low tire pressure indicator on the instrument panel. The amber LED that I'm talking about is on the center of the dash just above the traction control on/off switch. It is a simple on/off toggle that turns the system on and off.

Once again, the symptoms are the LED illuminates when I put the van in reverse; which indicates that the Tire Pressure System is turned off- not that I have low tire pressure. It doesn't do it when I go directly into drive. To re-enable it I have to press the on/off button twice.

The switch you're referring to is, I believe, the on/off and indicator for the parking aid system which uses ultrasonic waves to alert getting close to an object behind you when in reverse. When the "off" indicator light comes on as soon as you put it in reverse, it indicates that there is a malfunction with the parking aid system somewhere. It could be a sensor or other fault in the system. Only the ford dealers will have the correct type of scanner to determine the problem but the scan alone costs $100.00, at least at my dealership. The number of times you must push the button to get the light off is a sure sign of the condition I mention here. My wife's van has the same trouble but her's finally reached the point where it won't turn "on" at all, even when not in reverse. It may be the parking aid computer on her's.

Phil