brake switch

zen · #1 October 11th 2003, 09:11

this info was in superman's article, but it had to be taken down and can't find the info in previous posts. what are you guys doing for the brake switch in a 944 conversion?

I have 944 m/c and am re-running all of the brake lines. so:

1. what part did you use?
2. where did you mount it?

kdanie · #2 October 12th 2003, 23:30

I think most folks are using a stock VW switch in a "t" fitting at the back, before the lines normally split. I'm going to mount mine near the shifter with the Bias valve and park lock (no parking brake in my 944 rears, they came from the midwest and the salt killed the backing plates).
ken

zen · #3 October 13th 2003, 21:49

i decided to go with a stock switch and t-fitting (using the same one that is used on the rear to split the line again) just off of the m/c so i can just run it back into the stock wiring location.

MattKab · #4 October 14th 2003, 17:08

Zen,

The increased efficiency of the Porsche brakes on a Bug gives rise to a normal braking* fluid pressure much lower than stock.

When I upgraded my brakes, I watched my voltmeter display the volt drop due to the brake lights, at a significantly reduced amount of pedal effort. Pressing the brake pedal minimally to light the back up when approaching a Junction in the dark required pulling up MUCH quicker than the car behind. This suggested to me the stock brake switch is rated at a pressure specific to stock VW braking system. I'm not the first to experience this??

I fitted a microswitch to a bracket secured behind the head of the top m/c bolt, an M8 bolt in 1" of fuel hose is cable tied to the pushrod and is adjusted to put the brake lights on when braking in rolling traffic, just like everyone elses.

The microswitch is wired in parallel to the pressure switch and are connected so that either serves to ground the coil of a relay for reduced load on the switches. Nothing is butchered on the car. The relay can take a shared feed from the brake/horn live at the connecters near the brake fluid reservoir (late Bug) and this is where the two core wire connected to the microswitch terminates. A few piggyback and male spades prevent any cutting.

Do not overlook the response of your brakelights for safety's sake.

Matt

zen · #5 October 14th 2003, 19:30

point well made and taken. has anyone else experienced the same? any other solutions? nothing wrong with the one made, just curious what others are doing too.

kafer.chris · #6 February 1st 2004, 19:31

used a adjustable brake switch with a range of 0.5 < 5.0 bar bought from a local hydrolic suppliers same thread and there is a small screw on top to adlust the pressure..

jack up the front spin the disc get a monkey to eat peanuts and press the brake pedal till it binds on the disc !!!!

i used a contiuity tested as the light i.e....

when she bleeped the light was on adjust to suit the brakes

cost about £35 but worth it

am running 944 s2 brakes all round on a swing axle 72

chris

boygenius · #7 February 1st 2004, 19:58

What about a 911 master cylinder with the switches already in it. Shouldn't they be set for the correct pressure.??

MattKab · #8 February 2nd 2004, 15:28

Quote:

Originally Posted by boygenius

What about a 911 master cylinder with the switches already in it. Shouldn't they be set for the correct pressure.??

I've just checked in the GSF catalogues, all Porsche models use the same switch for the brake lights priced at £2.00 (no partnumber given).

GSF sell a switch for all Aircoolers priced at £3.50 !!!

Maybe they are different? :shrug:

Matt

kafer.chris · #9 February 17th 2004, 17:32

thats going to save me a few quid for the cabrio brakes
cheers matt

chris

paul_f · #10 February 18th 2004, 04:54

Using a relay isn't a particularly good idea, unless you are using an ultra fast non automotive relay, but regular automotive relays have a switching time usually around several milliseconds, which although doesn't sound a lot in an emergency situation on a motorway could mean that someone stuffs up the back of you.

It wouldn't be your fault, but I would prefer not to have to go through the hassle of going through insurance etc.

The standard switch can easily switch a pair of standard lights plus a LED high level light.

Paul

MattKab · #11 February 18th 2004, 15:20

How many msec does it take for the fluid pressure to build to throw the switch? longer still when system pressure is decreased..

The pedal will always move before the brakes. I have a rapid brake light using a microswitch. Relay is needed with the discreet switch I am using. I look at switches from pendulum pedal cars, but I've not yet seen anything I prefer to what I have now.

LED eye level brake lights are a wise move on any VW :agree:

paul_f · #12 February 18th 2004, 15:30

The pressure increase will be almost instantaneous ie <1ms, the time to switch with a relay will be between 7 - 10ms

MattKab · #13 February 18th 2004, 16:03

Quote:

Originally Posted by paul_f

The pressure increase will be almost instantaneous ie <1ms, the time to switch with a relay will be between 7 - 10ms

I won't argue msec with no solid numbers. I will argue my brake lights are quicker than yours

but not on the net..

Matt

paul_f · #14 February 18th 2004, 16:34

To be honest as long as you have LED centre lights then it won't make much difference as they are much faster - I was just being argumentative

MattKab · #15 February 18th 2004, 16:55

Quote:

Originally Posted by paul_f

To be honest as long as you have LED centre lights then it won't make much difference as they are much faster - I was just being argumentative

No, they are much, MUCH faster

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