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

[sugarwood]

113945515h

[pmax]

Originally Posted by sugarwood

I barely ever drive the 911 the last few years.

Don't despair.

Working on your car is still part of the hobby, Sugar.

I enjoy every minute of it, contortions and straining included trying to squeeze into small spaces while trying to thread a needle thru a hole.

Originally Posted by sugarwood

113945515h

What's up ?

Post a pic of your predicament.

[wazzz]

Originally Posted by sugarwood

No, it is fuse #7
https://imgur.com/a/p0rGOjM

My fuse is intact.
I will order a new switch

Yes, fuse 7 is absolute position. But this same fuse is labelled number 4 on fuse box I on factory diagram. That's why I mentioned fuse box I.

The complete fuse row is divided in 3 parts on the factory diagram. One that starts from windshield and bears no fuse box number on factory diagram, next one is fuse box I and has 10 fuses labelled 1 through 10 (amongst which number 4 is the fuse you are looking for), and the last one is fuse box II and has 8 fuses labelled 1 through 8.

[sugarwood]

Does the brake light switch removal potentially introduce an air bubble bleeding scenario?
What if the switch is fine, but there is an air pocket in the switch?
Is this possible under this design?

[sugarwood]

I switched out the 2 year old switch for a Beck/Arnley 201-1087 Stop Light Switch.
The brake light is now working. Was not air bubble or bleed issue.
So, the cheapo switches fail fast.
Can't remove front switch since its blocked by brake line.

What a nightmare of a simple repair.
Remove carpet, remove shield,
detach cross brace (annoying bolt access at bottom)
detach 2 hoses, detach electrical plug,

22mm switch is so blocked by stuff.
1/4 turn at a time.
Back on fire

Getting air hose re-attached was also a hassle b/c it's not clear if the underside is seated.
Electrical plug also gets in the way.
I also started to attach the cross brace to the wrong screw hole (for back shield)

[Ginger77]

I was glad to find this thread when I recently found out my brake lights only come on when I nearly depress the pedal to the ground. Meaning under light braking I have no brake lights.

I didn't cheap out since brakes are essential and ordered two ATE switches. My old and new 3 prong switches are all 24mm BTW. My car is a 1977 911S and reading this thread I had feared it was going to be horrendous. But honestly I was done in 20 minutes. Not much to get out of the way and using a straight and a box wrench I replaced one at a time. The switch near the booster dripped a bit but the one furthest from me did not. Anyway I made sure it was a quick out with the old and in with the new.

Once I was done I checked out the result and I was gutted to see the new switches made no difference! Mind you I checked with the engine off so no boosted brakes so to speak. How can this be? What is causing my brake lights to only come one that late in the pedal travel.

How do I fix this? Is my master cilinder failing and not building enough pressure? Can or should I install the early switch at the pedal since my pedal box has provision for this and jumper the wiring?

[Ginger77]

I may be jumping to conclusions but could it be that my master cylinder is failing and not building enough pressure for the switches to activate until I depress the pedal fully to the floor?