Diesel glow plug light

[Michelin]

I have a 2001 Passat Sport TDi 130 and i have noticed that on some occasions when i put the ignition on the glow plug light stays on for about 10 seconds and then when i start it the revs race up to about 1500 and then settle back down slowly.Most of the time it is fine the light goes off after 2 secs and the car starts and the revs are normal and the car always starts straight away and the performance is always excellent no probs .This has happened when the engine is warm aswell as when it is cold.The car is always perfect i was just wondering if anyone knew what this meant incase it was an early warning for something or is it nothing to worry about.This is my first VW so i just thought i'd ask a couple of questions to see if anyone could help

[Crasher]

Get a fault code scan done, you probably have a faulty coolant temp sender which is easy and cheap to replace.

[rjs1003]

Hi Michelin,
Did that fix the problem? I ask because I have the same symptoms (2003 Passat Tdi 130) and my local dealer said there was nothing in the logs which might explain it... they couldn't reproduce it at the time (though it's getting more frequent now...)

Thanks,
Bob

[Crasher]

If there is no code when the dealer scans it you probably have a faulty brake light switch.

[rjs1003]

Seriously? The glow plug light staying on might be due to a brake light switch? The thing that's making me question that one is... well, that my brake lights are still working correctly, at least, at the point I start the car/back out etc and when I arrive at work/home.
Bob

[Crasher]

The switch is a dual unit, one circuit for the brake lights and to the ECU and the other for the ECU only; it is part of the safety system. If both switches aren’t perfectly in sync, it will flash the glow plug light.