Hi, new here. I am trying to locate the brake light switch in my Yeti 2015 . It is not above the brake pedal where I thought it should be. The car has a knee airbag which I think would be in the way if the switch was there. It is hard to see up underneath the dash so I took a photo. Please can someone tell me where to find the switch.

Thank you Urrell but the brake light sensor (1) is not there. The photo shows the view looking up from the floor.

No 1 is the brake light sensor.
What is the problem, why are you looking for it?
Edit: It would have been handy if you said your car has a DSG.

Edited 24 December, 20214 yr by Urrell

No. 10 here? (view on computer, not phone to see all info)

LLLParts

Urrell sorry I don't know what DSG is. The problem is I suspect it may be faulty. After a spell of wet weather the EPC light comes on, then the brake lights are on constantly, the cruise control won't engage and the air conditioner won't get cold. After the weather dries up the EPC light turns off and everything works again. Please what is DSG.

Whino thank you, I will have a look to see if it is there.

Sorry Wino. Bad spelling

DSG -Direct Shift Gearbox

 

Without going into all the technical detail, essentially a variant on an automatic gearbox.

 

hope it helps.

TruckbusUK thank you.

I don't have a DSG.

Thanks TruckbusUK, I don't have a DSG then.

Sorry double post

On 24/12/2021 at 08:37, drifter1949 said:

 I suspect it may be faulty. After a spell of wet weather the EPC light comes on, then the brake lights are on constantly, the cruise control won't engage and the air conditioner won't get cold. After the weather dries up the EPC light turns off and everything works again.

 

I'm sorry but I can't answer you specific question but I'm wondering why with the symptoms you list you arrive at a diagnosis of a possibly faulty brake pedal switch. What inter-connectivity would you expect between cruise control and the air conditioning/climate control that they should both be affected?

 

It's been said many times on this forum that weird problems without a logical explanation often come back to a problem with the battery, which makes sense as pretty much everything relies on electrical power for proper operation. Could your battery - which if original is now 6 years old - be at the critical stage where in dry weather everything works OK but in wet weather the extra load of, for example, the wipers, tips it over the edge? Is it something as simple as one of the battery connections not being quite secure and giving imperfect contact made worse in damp weather? Does a spray of WD-40 or similar improve things? Have you checked the earth strap connections? Other can probably point you to where you'll find them but if you have loose or dirty connections that would tie in the problem being only after a spell of wet weather.

 

These are only my thoughts and I hope you find an answer to your problem.

Hi

 

Going back to Wino's post, this suggests that some models of Yeti are fitted with a brake switch actuated by hydraulic pressure rather than the mechanical movement of the pedal.  Both methods have been used for many years. The switch in the drawing appears to fit into the side of the master cylinder and should be easy to spot.

 

Gremlins after wet weather suggests a problem with something electrical which is exposed to damp, which is far more likely to be something under the bonnet (hood) rather than something inside the sheltered area of the cabin. It wouldn't be unreasonable for the brake switch signal to be used for purposes additional to the brake lights, so you might get odd effects if it is sensed that the brakes are apparently on when the car is being driven normally i.e. throttle not closed.

 

I can only suggest a thorough check of the wiring and connectors under the bonnet, with connectors removed in turn and the pins inspected for any tarnish or corrosion.

Think it's a hall effect sensor on the MC.

Given its position on the master cylinder between the outlets for the diagonal split braking circuits it will most likely be a PDWA sensor (pressure differential warning actuator).

 

I dont know of any PQ35 platform VAG vehicles that use a hydraulic brake switch but will be happy to learn otherwise, poor translations might once again have led to confusion.

1 hour ago, Austin 7 said:

It wouldn't be unreasonable for the brake switch signal to be used for purposes additional to the brake lights, so you might get odd effects if it is sensed that the brakes are apparently on when the car is being driven normally i.e. throttle not closed.

Several, among them, cutting throttle if brake pressed at the same time and cutting cruise control.
If wanting to dry brakes if wet, get up to about 20mph in 2nd release throttle, quickly and gently apply brake then add throttle to balance against brake. It won't work if applying brake after throttle as it will cut throttle.

 

I have read that the brake switch in fact has 2 switches, one for the brake lights and one to turn off the cruise control. The circuit diagram confirms this, there are 4 wires to the switch and 2 separate circuits. I forgot to mention also the engine power drops off temporarily and then returns to normal. I searched the Interwebs extensively and found numerous reports of the same symptoms. I have only had time during the busy Christmas period to have a quick look at the brake master cylinder  and I can feel the switch and wires underneath but can't see them. When I get time I will get a mirror to help see what I am doing or get my friends son to do it for me. I am aged 72 and can no longer go crawling around cars.

Thank you all for helping me find the location of the switch. I will report back when I can.

PS. The battery was replaced about 2 months ago.

Just a thought but did the problem occur just after the battery was replaced and if so could it be related - I know it's very unusual these days but a defective battery slipped through the checks? (Many years ago my mechanic told me of an owner who did his own servicing and had been going slowly crazy trying to trace a fault, replacing part after part at considerable expense. In desperation he finally took it to the garage. They eventually traced it to a new but defective spark plug put in by the owner as part of his routine servicing. Different plug, problem solved).

3 hours ago, Urrell said:

Several, among them, cutting throttle if brake pressed at the same time and cutting cruise control.
If wanting to dry brakes if wet, get up to about 20mph in 2nd release throttle, quickly and gently apply brake then add throttle to balance against brake. It won't work if applying brake after throttle as it will cut throttle.

 

 

It took me 2 years to work that one out Urrel, its the way that I prefer to bed in new brakes or deglaze them from time to time.

 

And I didn't even work it out, I read it on here, if it was you then thanks again 👍

 

Given that I always experiment to achieve what I want when a control system or ECU won't play ball I was very embarrased & humbled that I had not tried what now seems to be the obvious.

2 hours ago, drifter1949 said:

I have read that the brake switch in fact has 2 switches, one for the brake lights and one to turn off the cruise control. The circuit diagram confirms this, there are 4 wires to the switch and 2 separate circuits. I forgot to mention also the engine power drops off temporarily and then returns to normal. I searched the Interwebs extensively and found numerous reports of the same symptoms. I have only had time during the busy Christmas period to have a quick look at the brake master cylinder  and I can feel the switch and wires underneath but can't see them. When I get time I will get a mirror to help see what I am doing or get my friends son to do it for me. I am aged 72 and can no longer go crawling around cars.

Thank you all for helping me find the location of the switch. I will report back when I can.

I did not make it clear enough that the PDWA is not the brake light switch but a sensor to warn when there is an imbalance between the pressures in the two diagonal split braking circuits, usually caused by a leaking caliper seal.

 

I am very confident that the wires you have found on the master cylinder will not be for the brake light switch if your master cylinder resembles the one in the parts diagram, if anyone can prove me wrong then I will be delighted to learn but I don't want you wasting your time fumbling around in an inaccessible area & perhaps removing theconnector from the brake  failure warning system and perhaps not being able to reconnect it.

 

The switch and connector are normally in the dry protected cabin environment somewhere on the pedal box, it is indeed a double pole switch, one pair of contacts for the engine ECU, the other for the body control module (brake lights).

 

The clutch master cylinder does however have a reed switch to sense when the clutch is depressed.

Edited 26 December, 20214 yr by J.R.

I think the diagram in the catalogue is a little off, as the switch appears to mount on the underside (or a jaunty 45° angle maybe) of the MC when you look at listings like this Датчик включения стопсигнала VAG 8P0698459B для Skoda Yeti 2009-2018 в Москве (euroauto.ru).  

It's a brake light switch though, no hydraulic connections to be seen.

Brake Light Switch Škoda 5G0698459 (skoda-parts.com)

 

 

A fella changing one on a LHD Golf here, 

 

 

Edited 26 December, 20214 yr by Wino

Thankyou for that, I stand corrected 👍

 

Will be a pig of a job on a RHD with DPF, the clutch cylinder is difficult enough until you have done it 10 times then you can do it blindfolded, in fact its preferable!

 

Did you notice that he had destroyed the release latch on the connector? Hands up anyone who can honestly say they havn't done the same on another connector at some time!!!!

Edited 26 December, 20214 yr by J.R.

I poked my phone in underneath and found the little bugger, now I just have to wrangle the plug out and inspect the contacts.

20211226_142251.heic

20211226_142251.heic 

20211226_142337.heic

Hi

 

I didn't appreciate that it's a Hall effect sensor, i.e. it responds to a magnetic field. 

 

Presumably there is a magnet forming part of the moving internal part of the master cylinder, and the magnetic field extends out through the non-magnetic metal wall of the cylinder. 

 

A Hall effect sensor is essentially solid state, so will require a DC supply and may have its own onboard signal processing chip, i.e. it's not just a simple metallic contact switch.