Brake Warning Light and Rain?

[PorscheServiceThen529Plan]

I have an 01 C4. Just had PPI and $10k of service at dealer (that ruined the car seat leaving window open in rain) done 3 months ago with no mention of brake pad or rotor wear. Brake light came on first really rainy day in a while and does not clear turning car on and off . Light only came on briefly weeks ago only right after I washed the wheels. Dumb question probably but Before I start pulling wheels: is there a way to measure the pad or rotor thickness without removing the wheel or is the water causing a short - is that even possible on a 12 v circuit? Check other posts could not see anything about water. I drive in rush hour half the time and beat on the clutch and brakes pretty hard. What is enough thickness for pad and rotor, if I am within a few months of having to do it I will just do it. Read the DYI tutorial - is this pretty easy? Would love to get Suncoast parts and just do it instead of blowing another $2400 already. many thanks in advance

Edited November 12, 2013 by PorscheServiceThen529Plan

[Loren]

It is not a short it is an "open". The brake wear circuit looks for a broken connection. Usually this is when a brake sensor wire wears through - but i can occur if a brake sensor has a bad connection or a wire gets broken.

I think it best to inspect the brake pads and disc wear with the wheel off. You can also inspect (and even test) the brake sensors.

I think a good wheel wheel inspection is your next task.

[PorscheServiceThen529Plan]

Loren, thanks! It will be wheels off this weekend. "Open" Makes sense, I should have realized that based on what I read in other posts.

[Ronnie38]

Which window was open to the rain? Weird things happen when the alarm module gets wet it is located under the drivers seat. I don't think the brake pad sensors are routed thru it, I had a real hard time to follow a the circuits that pass though it. but any connector that gets water in it can do weird things.

[Richard Hamilton]

The wear sensors are in a loop, running from the instrument cluster, via each sensor, and back to the cluster. A break in the circuit, or a short to ground, will set off the warning light. It works both ways to make it failsafe.

However, you need to check the pad thickness to see if they are getting low. The sensors are about 4mm diameter, so once the pads get down to that thickness they wear thru the sensor, and the circuit goes to ground. If the pads look good, check the sensor connectors, as if water gets in they corrode, and the loop goes open circuit.

[PorscheServiceThen529Plan]

Many thanks for the replies and I will pull some wheels. The weird thing is that all three times the light came on when really wet and all three times the light goes off once the wheels have dried off. So its off now, but I will solve the mystery! thanks