06 Jetta TDI Clutch pedal switch/sensor?

[mirek07]

Recently I have to press very hard on clutch pedal to start the engine on my 06 Jetta TDI. Any idea what could cost this problem? Thanks!

[chittychittybangbang]

Only thing I can think of is bad clutch pedal switch. I don't know if it's on the top or bottom of pedal travel since I've never looked. I've never tried to jump the switch but I suppose it should be possible for testing purposes. For safety reasons, don't jump the switch for regular use.

EDIT: It looks like they changed the switch type on the mk5 cars, see the next post

[Ol'Rattler]

I know this one from my experience when I changed my clutch and had a similar problem. But first some education.

With the introduction of CanBus the A5 work quite a bit differently than the A4's. There is no switch in the usual sense for the clutch. What there is is an electronic sensor mounted on the outside of the master cylinder, under the hood that detects the master cylinders piston movement and sends an "OK to start" signal to the ECU.

Being that is a sensor and not a switch, it is sending a discrete signal to the ECU and trying to bypass the sensor probably won't make the car start and might even burn out the ECU in the process. My best guess is that the sensor works something like a Hall effect sensor.

With my car, what was happening was the slave cylinder was reaching the end of it's travel before the master cylinder piston was in "proximity" of the sensor. Another words, the clutch petal wasn't close enough to the floor for the car to start.

I found that If I pushed real hard, I was able to get the car to the start, but in the process, it overextended the slave, destroying it.

Could you give more info on your car such as miles on the clutch, how suddenly this happened and anything else you can think of?

At this point I would not think it is anything hydraulic. My best guess would be a loose slave cylinder, worn or damaged slave rod, a worn throw out bearing or a bent throw out bearing arm.

Almost forgot the obvious. Is there something blocking the clutch petals movement like a floor mat or wiring?

[mirek07]

This is 06 Jetta TDI 180000km clutch was changed in Oct. 2011 at 170000km.
This problem start 2-3 weeks ago and getting worst. Car is still starting with hard pedal press
and nothing is disturbing movement. The clutch itself fills and working perfect!
Thanks for great education and all info!!!

[Ol'Rattler]

You could check the master by having someone hold the clutch petal down with normal force and open the bleeder briefly and then close it. If the master is OK, the petal should sink the rest of the way to the floor to the start position. Without releasing the clutch, see if the starter will engage now.

Make sure they understand to hold the petal to the floor and not let up on it until the bleeder is closed.

You might have air in the slave. Bleed the clutch system and see if that helps. When you bleed, don't let the level in the reservoir get more than about 1/4th of the way from the top or you will be introducing air into the system.

Probably after that, you will have to remove the slave for further investigation............

[wasp]

it can be safely bypassed by grounding a purple wire somewhere. real helpful, i know. i did it for a remote start install (compustar) on a 5 speed and it works perfect. if this is of interest i'll try to find the link where i found the info. i think it was on the golf mk5 forum

[mirek07]

I will greatly appreciate if you can found it for me. Clutch is working perfect only trouble is starting.
If I can bypassed this sensor I wouldn’t worry about it for now.

[Ol'Rattler]

I'd like a better understanding of how this works, as well. My concern with the start sensor permanently bypassed would be that the cruise wouldn't work and the ECU would always be receiving a signal that the clutch is disengaged causing possible drivability issues.

I thought of bypassing the sensor when I had my clutch issues and decided the best option was to make the car operate as it was designed because of the issues I mentioned above.

I would say that if you do bypass the interlock, use a momentary switch so that you bypass the sensor to start and when you release the switch, the ECU will be happy and let the CC operate normally and also not think the clutch is always pushed in.