Correct but I was thinking about the contacts of the plug and socket.

Thanks

@drifter1949 are you familiar/well practiced at undoing the latches on these type of connectors? There's a 'knack' to it that's not completely obvious.

Edited 27 December, 20214 yr by Wino

No, especially since I can't get a good look at it.

Any tips?

I'm not near my computer to look for good photos/videos just now, but search for "vw connector removal" on YouTube and you should find a few useful results.

In words; push the connector body firmly onto the thing its plugged into while lifting the latch up a short distance in the opposite direction until you hear a click. Then pull connector away 

 

Find an easily accessible one to practise with. If you don't do that initial pushing, friction on the latch parts may cause breakage.

Thanks I will have a look.

Update.

It is indeed a pig of a job because it's a right hand drive and the plug is underneath and very close to the bodyworks. I was able to look through a narrow gap while manipulating a right angle pick and release the plug clip and then unplug the connector. I couldn't see any corosion on the contacts so I gave them a spray with inox and put it back together. To my amazement, the EPC light was gone an everything was working correctly. Then we had heavy rain overnight and the fault re-appeared the next day then came and went a couple of times over the next 2 days. I have ordered a new brake switch to see if that will fix it.

If you are still interested, stand by for the next installment.

Hi again

 

Some thoughts which might help.  Water is electrically conductive, depending on what's dissolved in it.  Rain water is near the least conductive end of the scale, muddy water in the middle and salty water near the most conductive.  In the UK they pile salt onto roads in winter, but we fondly imagine that it never gets below freezing in Oz !  Also, the effect it has will depend on the resistance/current of the circuit it's bridging across. So a traditional low resistance/high current circuit like a metallic switch and a filament bulb will be fairly immune, whereas a high resistance circuit like a logic line or bus circuit is more likely to suffer.

 

From your description, it sounds like the brake switch is tucked up away from any road spray coming upwards.  So it's a puzzle that the switch and its circuit seems to be affected by wet weather.  Probably worth checking that water isn't coming down from above, either onto the switch or any part of its wiring.  Sometimes wiring looms have multi plug/socket connections near where they go through the bulkhead, presumably to make things easier on the production line.  Such multi plugs can trap water if it drips on them or runs down over them when it shouldn't

 

My final thought is on a different tack, but stranger things have happened.  I wonder whether the brake switch lines run in the same loom as wiring to the wipers (front or rear), and chafing has occurred which is causing these two circuits to be bridged together.  As soon as the wipers are used, the brake circuit will be upset.  Alternatively, if they share a common fuse and there is a poor connection, interaction may occur.

 

Good luck with your quest.

Edited 3 January, 20224 yr by Austin 7

Austin 7

Thanks for your suggestions, I have worked in electronics many years and am searching for a circuit diagram at the moment. If the switch does not fix the issue I will certainly examine the rest of the system. I have read of so many like faults with the hall type brake switches that I will change that first.

 

I think the wiring is approx as follows, but without engine code I can't be sure.

Pin 1 at connector - N/C switch connection to engine ECU

Pin 2 earth to hall sender electronics

Pin 3 N/O switch (the one that indirectly controls brake lights) connection to engine ECU or BCM depending on date made etc.

Pin 4  (main relay) switched power feed from engine bay fuse 22 

 

The two switches are shown as both being operated by the hall sensor electronics, like this:

 

 

Edited 3 January, 20224 yr by Wino

The photo was very indistinct and difficult for me to see if it was from under the brake pedal or under the master cylinder, the subsequent talk about the hall sensor makes me believe it was indeed the master cylinder from the engine side, could you please confirm.

 

Forget that, after reading the previous posts and looking again at the photo it is now clear to me!

Edited 3 January, 20224 yr by J.R.

JR, I just noticed my phone photo is reversed left to right because i was using the front facing camera. It looks the same as the photo Wino posted earlier.

 

J.R. thanks for that info. I will take some measurements when the new switch arrives.

Exceptional weather event here, much rain and flooding and low motivation. I have noticed that even high humidity will bring on the fault. There is voltage at fuse 22 when fault is present. I found a Russian workshop manual online which says to remove brake light switch requires master cylinder to be removed. I dont want to do that myself so maybe I will look at making a special tool to reach the switch mounting screw.

But before doing that I will unplug the switch again to see if there is voltage to the switch socket. Or I might be able to probe the wires with a sharp point.

Well of course it stopped raining and the fault went away again so I got a scan done which reported fault no. P057100 - Cruise, Brake Switch (A) Circuit Malfunction. 

Possible causes of OBD code P0571 Skoda
– Misadjusted brake switch – Brake switch open or short circuit – Poor brake switch electrical connection – Failed brake switch The Error code is generally activated on detection of the following conditions: The P0571 Skoda codes is set when the stop light switch does not turn off even once the vehicle is driven.

Casting my mind back many years, I sort took an interest in this type of switch as I was looking after a late 2009 SEAT Ibiza that had that type of "brake switch", and so preparing for if/when I needed to sort it out.

I thought that at one point VW Group were selling a kit with both a new switch and a new sensor part - due it was suggested at the time that there might have been a slight misalignment issue, ie a slight design dimensional problem on some master cylinders - but remember that is just a "I think I remember reading" and not a fact based on experience.

 

Other possible issues with this switch's switching seem to have based on chaffing of wires - but in every case that I've read, which were all on SEAT Ibizas, the people that posted either never came back with a full description of what wires were chaffed/damaged and where, which is annoying, when their garage solved their problem, or in other's case, just a opening post - then gone for ever!

 

There used to be a "too long" bolt fitting into a body rail/stiffener that was said to cause some of these wiring issues, as yet I have never removed that bolt and cut it down to size to avoid that ever happening on my wife's 2015 VW Polo, or that late 2009 SEAT Ibiza or a 2002 VW Polo - okay only 2 of them had/have that hall effect switch on the MC, but I really should sort out that bolt as cables press against the tapered smooth end of that bolt, and that kind of annoys me!

 

Sorry not an absolute "do this" solution, but maybe food for thought.

 

You do indeed seem to be getting some horrible weather in that part of Oz.

rum4mo  Thanks for your input, every bit helps. It is frustrating when I get the time and motivation to have another look for the fault I have to catch it at the right time after rain and before it dries out again, my car lives outdoors.

Cheers

 

 

I just couldn't manage to change the brake switch so I took the car to a European car Specialist and the man changed it for me. Car worked fine for 2 days till it rained again and in the mean time the abs and traction control and power steering lights came on too which was fixed by fitting a new wheel speed sensor.

I have booked the car in again. I just hope they don't start throwing parts at it till they find the cause of the problem.