PSA: Check your brake lights. (and then get stuck trying to replace the switches)

[GH85Carrera]

Dang, I replaced my sensors without much difficulty, in not much time. The original OP has a car that has some non standard lines that are in the way, so it is more complex.

It is uncomfortable getting into position in the trunk, but as an certified old geezer it was not that difficult. Two sensors, and under an hour and I was done. To build a new brake switch never even entered my mind. What ever works for you is great.

[Kidasters]

Ha. I did this after someone told me they couldn't see my brake lights. The only other thing to add - have rags handy. Some brake fluid will come out when you do the swap.

[sugarwood]

Still waiting for the switches to arrive.
Last week, my brake lights would light up only with heavy pedal pressure.
Now, they don't seem to go on at all.

Tonight, I am going to short circuit the switch connector with a paper clip and make sure the switches are the actual issue, and not wiring or bulbs.

[thsupernge]

Bridge it with a test light probe?

[garment]

Sub'd

[garment]

I replaced my switches today. 40 min job, and that included removing the strut brace and some of the ducting to get at the switches. Deep 24mm socket for the forward-most switch, and the offset closed-ended wrench for the one closer to the dash. Bonus: the cabin brake light went out as well! Perhaps I should have believed the light a few months back...

[sugarwood]

Since my replacement brake lines were not factory routed correctly around the brake light switch,
I will need to detach the brake lines to remove the switches
(and flush the resulting air in the lines)

So, before I did all that, I wanted to verify it was a defective switch, and not bulbs/wiring.
Today, I jumped the switch connector and verified the brake lights illuminated.
So, yes, my switches are defective. Good to know before I take apart the brake lines.
This can be checked without removing hoses, just the front plate.

[John W.]

Sugar wood, That’s a good test before digging in. Been following your post since I have the same issue. Good luck.

[Bill Douglas]

Thanks Sugarwood, I need to do a replacement myself sometime soon. they seem to need more and more brake pressure each year I don't do it.

[sugarwood]

Got the wrong switches delivered. They had a different part number and the ones I got had a 3rd plastic prong in the middle and were sized at 24mm, not 22mm. Will send the parts back.

While I was comparing, I realized this job is beyond my ability. Nothing worse than encountering stupid PO repairs that are not stock. Taking apart that brake line seems near impossible. I barely was able to seat onto the nut an 11mm flare nut wrench. But, when I got it seated, the brake line blocked the sweep path of the wrench. There is no room to seat the wrench on a different nut flat. So, I have no clue how anyone can detach the brake line. I will leave this repair up to a professional.

[thsupernge]

I have that one too, I cut the plastic off and installed it. I think its the same part other than those things...

[thsupernge]

So I went about changing switches last Friday night. Wow, about 2.5 hours later and I had it completed. The access is really difficult as others have described. I did use the sensor test lead idea to make sure they worked correctly first and they did so I proceeded.

The best way I found was to remove the vent hoses first and make the clearance you'll need for the tools. I actually found that a 23mm worked best for removal as the 22mm was way too tight to work with reasonably. The back sensor had to be turned about 45 deg at a time so it was really slow going.

Once out, the sensor BLED brake fluid! Be sure to have tons of rags and/paper towels ready to roll. My master drained approx 50% of its fluid while I changed these. That wasn't necessarily a bad thing (my fluid was awful) but it goes everywhere and isn't easy to chase inside the car (frunk). Once the mess was cleaned up, the towels and rags tossed I noticed a big difference in pedal travel to brake light activation. Previously it would only activate if you were standing on the pedal. Now it is about 40% of the pedal.

[sugarwood]

That is a good photo of the correct stock brake line routing with a 90 degree bend.
Mine has no such bend around the switch. How did the switch prong get so bent ?

With your new switch, did you cut off the entire plastic cover, or just the plastic 3rd prong?
What did you use to cut off the plastic? Were your new switches 22mm or 24mm?

[thsupernge]

Originally Posted by sugarwood

That is a good photo of the correct stock brake line routing with a 90 degree bend.
Mine has no such bend around the switch. How did the switch prong get so bent ?

With your new switch, did you cut off the entire plastic cover, or just the plastic 3rd prong?
What did you use to cut off the plastic? Were your new switches 22mm or 24mm?

It Was bent reaching back to the farthest switch-this is a shot of the old switches.

I just took a jigsaw and removed the tab, filed it down a little, being sure not to go into the plastic "seal" and then connected it. One was 22 and one was 24. Not my favorite way to do it but that what I ended up with the time and I knew they'd work.

[sugarwood]

I'm trying to envision how you got a jigsaw blade around the metal prongs..

For others, here is the 3rd plastic prong in question.
Looks like the wrong part to me.

https://www.pelicanparts.com/More_Info/113945515HM14.htm?pn=113-945-515-H-M14&bt=Y&fs=0&SVSVSI=#tab1

[911pcars]

The decision for Porsche to switch from a mechanical to a hydraulic brake switch must have been an economic choice. Ideally, you want the brake lights to energize when you step on the pedal (adjustable), not when the hydraulic pressure reaches a set threshold (not adjustable). They’re not equivalent.

There’s a large variety of mechanical switches, all adjustable depending on actuation distance. Install in any convenient location in the pedal actuation system. The brake pedal and link to the MC are often used locations.
https://www.amazon.com/universal-brake-light-switch/s?k=universal+brake+light+switch&page=2&qid=1616524224&ref=sr_pg_2

If for some reason, you prefer an adjustable hydraulic switch, here’s a variety:
https://www.google.com/search?sxsrf=ALeKk00B8re8yhaq-AyU7TBIlvquRN475g:1616524682729&q=Mechanical+hydraulic+pressure+switch&sa=X&ved=2ahUKEwjq7O_bh8fvAhXAGDQIHQz9CHYQ1QIwFXoECBAQA Q&biw=1403&bih=877

[walt]

I replaced the hydraulic switches in mine and felt the pedal pressure was still to high for comfort. Adding mechanical switches to both my 911's is one of the best and easiest upgrades I've made.

Never considered an adjustable hydraulic switch but sounds like an interesting alternative.

[thsupernge]

Originally Posted by sugarwood

I'm trying to envision how you got a jigsaw blade around the metal prongs..

For others, here is the 3rd plastic prong in question.
Looks like the wrong part to me.

https://www.pelicanparts.com/More_Info/113945515HM14.htm?pn=113-945-515-H-M14&bt=Y&fs=0&SVSVSI=#tab1

Easy

[sugarwood]

That blade is wider than the gap between the prongs.
Since you had to saw diagonally, I am guessing you were not able to cut it flush?
No seatment issues ?

[sugarwood]

Took another stab at this project today, but was defeated again.

The front one is basically impossible on my car, due to brake line issues.
But, I figured I would try to replace just the rear, and get the car road worthy, at least.
You just need one switch to work.

I planned to flush cutter the middle prong and make it fit.

I moved the hoses even more and I was able to get a 22mm offset onto the rear switch.
Half way out, I realized the replacement switch is 24mm.
Well, I don't have a 24mm offset wrench.
And a 24mm deep socket doesn't have clearance.
Largest regular socket I have is 22mm.

So, I aborted and tightened the old 22mm switch.
I will return these 24mm switches and pay the $70 at the dealer for the right kind of 22mm.