Brake warning light and switches

[67westy]

My brake warning light has had a habit of randomly flickering on over the past few years so I decided to have a quick look this weekend, safety first and all that.

It looks at some point the master cylinder has been changed to one that takes 2 switches although the switches themselves are the 2 pin variety:

I'm guessing the solution is to change to the 3 pin switch and change the wiring to suit. Is there another option I'm missing?

Cheers

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[ozziedog]

I didn’t know there was such a thing on Earlies :msn4: :shock: :shock: :msn4:

Ozziedog,,,,,,everydays a schooly day :mrgreen:

 

[67westy]

I didn’t know there was such a thing on Earlies :msn4: :shock: :shock: :msn4:

Ozziedog,,,,,,everydays a schooly day :mrgreen:

I think it depended on where it was being shipped to, more of a US thing?

I've ordered some 3 pin switches now, managed to find some febi.ones rather than the unbranded versions from the normal suppliers

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[Moseley]

Hi Adam, isn’t your setup correct as it is? This is the wiring diagram from Bentley which would be for a US bus. I followed this when re-wiring ours and that also had a dual offtake master cylinder with two pressure switch ports, both with 2-wire switches (J1 in the below).

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[67westy]

Hi Adam, isn’t your setup correct as it is? This is the wiring diagram from Bentley which would be for a US bus. I followed this when re-wiring ours and that also had a dual offtake master cylinder with two pressure switch ports, both with 2-wire switches (J1 in the below).

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Hey that's the diagram I was looking at but I don't seem to have J4, I assumed that was also on the master cylinder but maybe I was wrong? Do you have that anywhere?

I think mine goes directly to the brake warning light but i might need to check again ...

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[67westy]

Also found this diagram but not sure where the switch is meant to be

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[Moseley]

J4 is the dash warning light - the red one on the instrument cluster that you press and should illuminate if the circuit is functioning correctly.


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[67westy]

J4 is the dash warning light - the red one on the instrument cluster that you press and should illuminate if the circuit is functioning correctly.


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Nope that's K9 on the cluster

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[Moseley]

Actually, now I’ve said that I’m not sure that is correct, as there is K9 shown as the warning light.

So now I’m stumped, I must have just ignored that and gone from the second switch back to the dash light.


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[67westy]

Actually, now I’ve said that I’m not sure that is correct, as there is K9 shown as the warning light.

So now I’m stumped, I must have just ignored that and gone from the second switch back to the dash light.


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I think that's how mine was wired and I don't think it would ever work no idea why it occasionally flashes now, probably a bad connection. The 3 pin switch takes on the role of the 3rd switch in the early setups

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[Moseley]

Do you know what the function of the dash light actually is? Looking at the wiring diagram, it would only ever light up when J4 closed... which would be every time you pressed the brakes?

I’m clearly missing something!


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[sparkywig]

Have you looked through this?

https://www.thesamba.com/vw/forum/viewtopic.php?t=694415&highlight=1968+brake+warning+light+on+dash

 

[67westy]

Have you looked through this?

https://www.thesamba.com/vw/forum/viewtopic.php?t=694415&highlight=1968+brake+warning+light+on+dash

I hadn't come across that yet nice find. I also found this that offers a bit more explanation: https://www.thesamba.com/vw/forum/viewtopic.php?t=587777&view=next

So I think as I don't have the plunger switch or appropriate master cylinder the 3 prong switch is the way to go. Will have a try at wiring them up when they arrive

Do you know what the function of the dash light actually is? Looking at the wiring diagram, it would only ever light up when J4 closed... which would be every time you pressed the brakes?

I’m clearly missing something!


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So the dash light should come on if one of the circuits fails, so there is no pressure at either (or both!) switches. I think the key to understanding the 3 switch setup is this bit from Sparkywigs link: "the switch on a 68 (J4) is a pushbutton like a reverse light switch opposed to a pressure switch, the master cylinder had a separate spring centered piston on the side that each hydraulic circuit pushed on from opposite ends, if one failed it moved the piston and the switch was activated."

Cheers

Adam

 

[Moseley]

Both really useful links, and makes sense now! 3-pin switches it is then for a functioning dash light...


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[67westy]

If you do go that route I read some bad things about the cheap 3 pin switches that most places sell. I managed to get 2 Febi ones (part 46024) from opieoils but they are out of stock now. Worked out about £12 each. You can get some ATE/FTE ones but they are silly money

 

[mike202]

My master cylinder was new in 2013 from JK and is a 1970 only part. It has just one brake light pressure switch which is three pin, however only two wires are connected.
I always thought that because the red dash warning light lit when I tested it by pressing it, that it was all fine and working. I am not so sure now [emoji3166]
Why do most master cylinders have two brake light switches? Since 2013 I have had a remote servo fitted 2017, and the brakes are quite good.

 

[67westy]

My master cylinder was new in 2013 from JK and is a 1970 only part. It has just one brake light pressure switch which is three pin, however only two wires are connected.
I always thought that because the red dash warning light lit when I tested it by pressing it, that it was all fine and working. I am not so sure now [emoji3166]
Why do most master cylinders have two brake light switches? Since 2013 I have had a remote servo fitted 2017, and the brakes are quite good.

Hey Mike,

I assume it's dual circuit? You would normally have one switch for each circuit to give redundancy, have you got a pic of it? I'm wondering if it had a blanking screw in it for the other port. I would say with a 2 prong switch your warning light definitely wont work aside from pressing to test it

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[67westy]

This one?

https://www.justkampers.com/vw-t2-bay-window-parts/t2-bay-braking-system-parts/brake-master-cylinders-wheel-cylinders/211-611-021-t-brake-master-cylinder-vw-t2-1970-only-non-servo.html

The wiring diagrams show 2 switches for a 1970 so not sure why it would only have one

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[67westy]

And the heritage one shows two ports for brake switches https://www.heritagepartscentre.com/uk/211611021T-brake-master-cylinder-left-right-hand-drive-without-servo.html

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[mike202]

Yes that’s the one. It’s actually come down in price since I bought it 7 years ago from Just Kampers [emoji849] [emoji23].

I assume it’s a dual circuit one because it has the two feeds from the reservoir above it and two brake lines coming from it.