Mark Buchanan

Hi,

I have a 1988 911. The brake lights don't come on until the pedal has been pushed to nearly half way down (by then, the car is screeching to a halt, fast). This is a dangerous condition in normal street driving. Pressing the pedal hard enough to illuminate the brake lights could cause me to become someone's hood ornament, especially in New Jersey heavy traffic (stop & go).

I thought that bleeding the brakes might solve this problem, but it didn't help. The pedal is not soft and the brakes bite *hard*. The previous owner had Super Blue brake fluid. I replaced it with Castrol Synthetic thinking that may have contributed to the problem. Comparing it to my 968, the brakes work extremely well, even though the lights don't agree.

I read that the system that illuminates the brake lights is hydraulic but I have no idea if there is any adjustment that I can do? Any ideas?

Thank you in advance,
Mark

Amber Gramps

Mark, this is one of the first things I did to my car. I've gotta get my lap top out cause the wife want this computer, but I'll walk you thru in a sec....

theiceman

there are 2 switches on the master cylinder, replace them.

Amber Gramps

....and there you have it. Works every time.


the system in redundant but you really should do it right and raplace them both while you are in there. Don't get the ones at the local parts store unless you have a VW supply house locally. They can be found quickly using "brake light switch" at www.automotion.com on the '88 you will have the 2 prong version. they are $8.95 ea

Mark Buchanan

Thanks so much for the replies, it's so much appreciated!

DRACO A5OG

Hey Mark,

So how is your Brake Lights now?

scarceller

The brake light switch topic comes up a lot on the 84-89 Carrera. I also have brake lights that are slow to come on, meaning a light press of the brake pedal does not turn them on. But they do work if you press the pedal moderately.

IMHO - I'm not sure why Porsche Engineers designed the brake lights to operate from pressure in the brake fluid? I'm sure they had a very good reason for this just not sure what it was?

But it's interesting that in the 993 they went back to mechanical switch on the pedal this to me seems to indicate that Porsche felt it may be a better design, just a quess here.

At any rate I personally would prefer and am going to alter my 84 Carrera to a manual switch on the pedal. I may just wire it in parallel with the existing fluid driven switches.

The question is howto mount the new mechanical switch?
Looking for ideas here, has anyone done this?
Would the 993 pedal cluster work in the 84-89 Carrera? I saw the cluster for sale on ebay not long ago but did not know if it would/could be used.

I really think a mechanical switch will function and bring the brake lights on much quicker and I'm all for safety.

Amber Gramps

You have two switches on the master cylinder as a fail safe. this also effects the cruise control function. No brake lights, no cruise control so you may have issues there. When for less than $20, you can fix it and fix it right, I wouldn't change a thing.

Marty916

Had the same problem with my '87 targa. It was the two pressure switches as mentioned above. I picked up replacements at a local parts slinger. Make sure you get the switches without the small divider between the two electrical posts or your plug won't seat. When replacing, have an assistant apply light pressure to the brake pedal so you won't introduce air into the system when removing/replacing the switches.

DRACO A5OG

Gentlemen,

There is a fix without any hacking into or permanent modifcations to the BLS system pre '89 P-Cars. It is a Plug and Play device. One can always go back to OEM for Concours reasons or Just wanting to Burn Out some BLS's, JKD.

You see Porsche's habit of over engineering, designed in too many amps to service the BLS's resulting in BLS Slowing or worse BLS Failure.

Swapping out the BLS is a temporary fix but the slowing of the BLS will return.

Even though I am far from Concours, placing a mechanical switch is not acceptable to me and the way our P-cars were designed albeit faulty design.

As Requested by a Rennlist Member via PP Forum, I was trying to post in the Classifieds but I am a Lowly Basic Rennlist Member so I am unable to share my company's final solution to the Faulty BLS.

If anyone is interested please PM me

jester911

So does this mean your not able to post here your solution? Are you selling a solution?

Just trying to figure out what it is you are telling us.

scarceller

One theory seems to be that the switches are going bad because the current draw (AMPS) are to high. So one simple solution is to put a relay in so that the Brake Switches simply pick the relay.

I however think there may be more issue(s) with these switches than simply current draw. The relay of course can't hurt.

I'm going to put a mechanical switch in my car right at the Brake pedal, I just feel much safer with a simple mechanical switch rather than switches driven by fluid.

I will still keep the 2 stock switches in place and just parallel the mechanical switch to the existing 2. Basically if you do this you have 3 fail safes.

The relay idea is also great and I may do that as well. Brake lights are important and I'd rather be safe.

Just my thoughts on this.

jester911

I don't think I buy the amperage draw being to high. The fuse would blow or the switch would stop all together if it were an electrical problem. The usual issue is it takes more pressure to activate the switch and again that is not an electrical problem.

I think from what I have seen the problem is sub-par replacement switches have been used and that is why it seems to reoccur more often.

I changed my switches over 5 years ago and haven't had any issues with them since. YMMV

DRACO A5OG

Yes, indeed my company is producing and selling the Solution for Faulty BLS's but I am trying to follow forum rules and not make this thread a sales pitch. For those whom are interested they can PM me discreetly.

As far as non-OEM or Cheap Overseas After Market BLS's, with our device this can be avoided:



Cross Section of a BLS, Note right side



I too was skeptical that PAG would tolerate such a design flaw and thought maybe it was a cheap BLS the POs may have put in my baby. Well low and behold it was the OEM BLS. I searched like a insane idiot for a Hi-Performance low pressure BLS's but my Engineer pointed out the issue. Enough said I developed our device.

scarceller

I'm all for keeping my 84 Carrera stock but I do have slow brake lights. I just ordered 2 new switches from here:
http://www.joetlc.com/brake-light-sw...o-p-16814.html
$5.00 each

I plan to start by changing these and adding a relay to the brake lights to reduce the current through the switches.