06 Jetta TDI brake Switch

[Hrdc0r19]

I was having dragging brakes, the pedal was falling, and I could only fix it by putting my foot beneath and lifting the pedal up. I fixed the issue by replacing the master cylinder and the brake booster. Now I have an implausible signal from the brake switch. I replaced the brake switch, the one on the master cylinder I don't have one on the pedal. Still have an implausible signal. I'm still pretty new to Vag-Com, but it looks like my switch is working. The warning lights are toggling on and off with the Glow Plug Light. The brake light switch goes to activate while pressed, but then goes to Non Operational when it's not pressed. Did I get a bad switch or is there a problem with my master cylinder? Why on earth did they move it from the pedal? My brake lights never turn off and I can't use the cruise control.

 

[Seatman]

Switch should be up top where it gets hit by the pedal, way up under the dash in an awkward postition. Not on the pedal itself.

As per this video

 

[sptsailing]

I don't remember the details, but these switches are weird and in many cases cannot be removed and re-installed. I had to buy a new one due to whatever the issue was.

 

[Hrdc0r19]

That is not how mine is. I'm not sure if it's because I have a TDI or maybe it was a mid year change. Mine is on the master cylinder and there is nothing on the pedal.

 

[Seatman]

On my 2007 before refitting I had to set some tab thing to allow the plunger to fully extend, then when you fit it and clicked it into place it locked itself at the correct adjustment.

Never seen one on the master though so no idea how they work.

 

[Vince Waldon]

Pictures of this would be pretty helpful, as a master-cylinder-mounted brake light switch is certainly an exception rather than the rule.

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[Hrdc0r19]

This is the underside of the brake master cylinder.

 

[Rx7145]

Interesting. It looks like without stability control has that switch on the master cylinder.
With stability control doesn't seem to have it.
This is from looking at the RockAuto catalog.

 

[sptsailing]

Looking at your VCDS pics, I see an ABS error code. Perhaps there was a brake bleeding error of some sort that has something to do with the issue. I do know it can be difficult to get the air out of the line to the clutch if you have a manual transmission. I also seem to remember warnings about being careful not to get air into the ABS control as that would cause problems. I only work on my VW when it is broken, and it has been working correctly quite awhile since that was the case, so I do not remember all the details of my brake system repair travails.

 

[Hrdc0r19]

The ABS Brake error is implausible signal from the brake switch. I had a little problem with bleeding the clutch, but not too bad.

 

[sptsailing]

When I was having brake issues, the dealer was recommending replacing both the vacuum booster and the master cylinder with parts different from the original part numbers, as they informed me that the original booster part number was no longer available and that the new booster type required the new master cylinder type as well. The newer master cylinder type had the brake switch on the master cylinder instead of by the brake pedal like the one I had. This meant that it would require a different wiring connector, as the connectors were not in the same place. That in turn suggests wiring modification may have been needed, which in turn suggests no end of problems, as these are VWs which frequently have electrical issues. Doing work in the engine compartment with wiring involved may well have made some sort of issue, so I suggest thoroughly inspecting any wiring related to the brake light switch, including inspecting grounding wire connections thoroughly. I am not an expert VW mechanic, so these are just conjectures on my part.

 

[Seatman]

How does that switch work? Some sort of magnetic signal through the master or something?


First time I've ever seen that

 

[sptsailing]

How does that switch work? Some sort of magnetic signal through the master or something?


First time I've ever seen that

I believe it is simply like an oil pressure sensor.

 

[Rx7145]

I think it works like a proximity sensor that it senses the steel under the aluminum. That’s my guess anyway.

 

[Vince Waldon]

Yup, I don't see any fluid passage between the master and the sensor... just a mounting bolt.

Very interesting!

 

[Seatman]

Weird one for sure, how are you meant to test it? I like the good old fashioned press the plunger to see if it works lol

 

[kathie659]

I was having dragging brakes, the pedal was falling, and I could only fix it by putting my foot beneath and lifting the pedal up. I fixed the issue by replacing the master cylinder and the brake booster. Now I have an implausible signal from the brake switch. I replaced the brake switch, the one on the master cylinder I don't have one on the pedal. Still have an implausible signal. I'm still pretty new to Vag-Com, but it looks like my switch is working. The warning lights are toggling on and off with the Glow Plug Light. The brake light switch goes to activate while pressed, but then goes to Non Operational when it's not pressed. Did I get a bad switch or is there a problem with my master cylinder? Why on earth did they move it from the pedal? My brake lights never turn off and I can't use the cruise control.

not sure if applicable to your vehicle, mine (2001) was under recall for brake switch

 

[sptsailing]

If it is a proximity switch involving magnetism, perhaps it can be tested by using a powerful magnet near it to see if the brake lights are affected.

 

[Rx7145]

If it is a proximity switch involving magnetism, perhaps it can be tested by using a powerful magnet near it to see if the brake lights are affected.

You could try that, but if it’s what I’m thinking any carbon steel moved close to the sensor should trip it.

 

[sptsailing]

I found a VW related video about this.
Brake light switch bench test (Hall Effect brake switch)

 

[oilhammer]

LOL.,... took until post #20 for someone to figure out it is a Hall sender switch, and completely different than the earlier type ones on the pedal.

 

[Hrdc0r19]

That's a great video, thank you! I ended up putting the original brake switch back on and it works now? It was having an intermittent issue that hasn't come back. The aftermarket brake switch never worked.

 

[Seatman]

LOL.,... took until post #20 for someone to figure out it is a Hall sender switch, and completely different than the earlier type ones on the pedal.

Good of you to comment that earlier

 

[oilhammer]

First time I saw the thread!