brake light switch

[martiniqueln]

I have to press down really hard for my brake lights to go on and my wrench tells me it is a pain to change but this is probably the cause .
Any ideas on Doing it myself ?

How hard is to change the brake light switch on the master cylinder on my Porsche .

911 , 1989 3.2

[scottb]

There are two switches on the left side (as you look at it from the front of the car) of your master cylinder. It takes about 30 minutes, tops, to replace both of them. It's very much a DIY job, and our host sells the parts. If your wrench says it's a PITA to do the job, find a new wrench.

Do a search here on the board and you'll find dozens of threads on this subject.

[martiniqueln]

What if it is the brake light switch under the pedal ?
I have cruise control .
Is that one harder to change ?

[scottb]

If you have an 89, the brake light switches are on the master cylinder (unless someone has done a custom job and put the switch under the pedals). Go outside and look at your car. You'll see the two switches on the left side of the MC.

[martiniqueln]

Do I need to bleed the brakes when I change it ?

[scottb]

That's an open question. Some people say yes, others say no. I didn't when I replaced my switches, and the brakes are fine. YMMV.

[Por_sha911]

Scott is correct. It isn't mechanically difficult, just a hassle to get in there. I did it with a friend in an afternoon (including bleeding all 4 wheels and the clutch as well). Do a search and you will find several posts about it. There are some really good tips on what to do. Replace both switches.
Do you have to bleed the brakes? Probably not but it is a good idea since you are opening up the system. You can bleed the brakes with a pump or a friend. Again, search button is your friend.

[rcecale]

+1 to what Joe and Scott said.

I just replaced mine this past weekend. A Pain In The A$$ to get access to them, but once you're there, it's pretty simple.

You need to pull the carpet forward and remove the big cardboard panel. It's held on by 4 phillips head screws.

Once you have that off, you'll want to disconnect the two vent hoses and move them out of the way. Just a couple of hose clamps here, no big deal.

There is also some sort of brace that runs from the top-center of the opening, to the floor. This was held in place by a 10mm bolt on each end. The top one, no problemo..the bottom one...well, let's just say it was such a PITA that it came really close to making me say to he!! with putting it back in. Stick with it though, you'll get it.

Here are a couple of pics to show you exactly where the switches are located.





The switches can be easily removed with a 22mm deepwell socket. If you don't have a 22mm, a 7/8" deepwell works just as well.

Before you remove them, stuff a dry rag underneath them to catch any dripping fluid...you don't want to get that stuff on your paint.

Loosen a switch with the socket but don't remove it until you have the replacement out of the box and ready to go. Then, remove it and slip the new one into place. Do the same for the other one.

You'll drip a little bit of fluid out of the port, but it shouldn't come gushing out. The rag should have no problem catching all the fluid.

Since you shouldn't lose too much fluid, you shouldn't need to bleen the brakes: I didn't and my brakes show no noticeable difference. Keep an eye on your Brake Fluid Reservoir so you have an idea how much fluid you lose.

Figured I'd doctor this pic up to show you the brace I was talking about earlier. The brace itself seemed pretty straight forward, the problem was a small section of rubber tubing in front of the lower bolt. I didn't want to remove that because it looked like way too much brake fluid would come out, necessitaing the need for a full system bleed.





It took a bit of effort (okay, more than 'a bit"), but I finally got the thing on by holding it in place with my finger while at the same time, pulling the tubing aside enough to get a 10mm wrench on it.

Have fun!!!

Randy

[gtc]

Excellent job on the how-to, Randy. It helped me out enormously - especially since Bentley doesn't have anything.
Just a few notes on my replacement:
1. The brace that Randy had such trouble with was no problem for me. There was some kind of electronic control box attached to it, which I had to remove and lay aside during the procedure.
2. My ratchet and socket was too big to fit onto the rear switch. THAT was the real PITA for me.
3. My '84 Carrera has the narrow two pole connectors. Rather than track down the elusive "adapter" Pelican suggests, I simply pulled the spades out of the plastic connectors and attached them straight to the switches. Works fine.

[9dreizig]

thanks Randy!! just helped me out a bunch too!

[RoninLB]

some press on pedal w/ switch cracked to flush out any crap building up.

[Formerly Steve Wilkinson]

One thing that I've heard you're supposed to do, in order to eliminate the delay between touching the brake and the brake lights coming on (which seems to be an endemic 911 problem), is pre-fill the new brake-light switches with brake fluid before installing them.

Didn't make any difference for me, though maybe I didn't do it correctly: the brake lights still require a tad more-than-acceptable pedal pressure to come on.

I solved the problem by installing a pair of self-contained (battery-operated) multiple-LED motorcycle taillights that are very bright from directly behind and that pulsate when they come on. I mounted them under the rear wing with Velcro and set them so they come on the instant there's the slightest decelerative force. (They're mercury-switch activated.)

[rcecale]

Originally posted by gtc
2. My ratchet and socket was too big to fit onto the rear switch. THAT was the real PITA for me.

That actually started off being a PITA, so rather than using a ratchet wrench, I used a speed handle with a swivel adapter on it...the switch came right off.

Randy

[agip]

thank you, very helpful info.

[4flyboy]

Originally Posted by Formerly Steve Wilkinson

One thing that I've heard you're supposed to do, in order to eliminate the delay between touching the brake and the brake lights coming on (which seems to be an endemic 911 problem), is pre-fill the new brake-light switches with brake fluid before installing them.

Didn't make any difference for me, though maybe I didn't do it correctly: the brake lights still require a tad more-than-acceptable pedal pressure to come on.

I solved the problem by installing a pair of self-contained (battery-operated) multiple-LED motorcycle taillights that are very bright from directly behind and that pulsate when they come on. I mounted them under the rear wing with Velcro and set them so they come on the instant there's the slightest decelerative force. (They're mercury-switch activated.)

---------------------------------------------------

Don't mean to hijack, Steve do you have a link to what you use? Thanks, Scott

[dan88911]

Here's an option.
Carerra / SC mechanical brake light switch install.

[dan88911]

Brake Light Switch Question

[2thVet]

Thanks for all of the knowledge and advice in this post- going 16 years back now! This was one of the first projects I recently tackled on my newly acquired 88 Targa.

I found that cutting off the plug ends of the old switches before removal (with a small tin snip) allowed me to fit my wrench and ratchet in the space (and over the end of the switch) much easier. Placing and tightening the new switches was easier than removal of the old ones, IMO.

[Noah930]

I came across this thread last week because my brake lights ('87) wouldn't come on. It wasn't the bulbs. It wasn't the fuse. So I found the brake light switch in the frunk, pulled the connector, jumpered it with a bit of wire, and stepped on the brake pedal to confirm it was the switch that was faulty.

Based upon another thread here in Pelican--a thread which I can no longer find--I used ATE replacement switches purchased from our host. If you go the ATE route, just note they take a 24 mm socket/wrench (whereas stock is 22 mm), and there's a little white plastic prong in between the two metal ones that has to be broken off to fit the 2-post connector wire. Just break off the plastic blade, no need to remove the entire white part. But most importantly, the switch threads right into the master cylinder just fine.

[rnln]

Too small of a job for him to charge

Originally Posted by scottb

There are two switches on the left side (as you look at it from the front of the car) of your master cylinder. It takes about 30 minutes, tops, to replace both of them. It's very much a DIY job, and our host sells the parts. If your wrench says it's a PITA to do the job, find a new wrench.

Do a search here on the board and you'll find dozens of threads on this subject.