tone40

'88 Carrera.

The brake lights only work intermittently, only when I push very hard on the pedal.

I replaced the circuit fuses and checked the fit on the 2 brake light switches. No change.

Can the fix be?: (1) The brake switches or hydraulic components of the switch sending units are bad. Can each separately or both of the 2 assemblies go bad? If the sending units are bad, is the hydraulic system opened (i.e. catch escaping fluid and bleed system)? (2) The brake pedal rod needs adjustment. There is about 1/2" of free play before resistance is felt. The light only comes on when the pedal is bottomed out hard, about 1-1/2" of travel. (3) The hydraulics need bleeding. The pedal pressure is not soft or spongy.

Thanks.

Ed Hughes

I'd say that unless you had the whole thing apart, the rod didn't fall out of adjustment. I'd replace the switches, they're pretty cheap and a known consumable, and easy enough to change.

User 4221

IIRC, the switches are pressure activated. It is possible they are failing and showing the symptoms you mention. They should be replaced as a pair since they are wired in parallel.

tone40

Is the failed part the white electronic component or the metallic part that fits into the side of the master cylinder? If it is the metallic part, will I have to re-bleed the system?

User 4221

I replaced these years ago on my 928.

I don't recall needing to bleed afterward but YMMV.

Ed Hughes

I did mine with a new M/C, I cannot remember if they are exposed to the fluid or behind a membrane or something?

User 4221

IIRC, they are exposed to fluid and have a small orifice that allows fluid into the pressure membrane on the switch.

Jim @ EuroWerks

Seldom do you have to bleed after replacement. Both have to be working correctly to carry the current. Replace them both. Use you catch rags, you will loose very little fluid. Thats how they act when one is acting up. Never seen anything "clogged" inside to cause it. But I'm sure it would if something was really in there. Probably not. Get the switches.