Edward

So with regard to the two pressure switches at the master cylinder that actuate the brake lights: why are there two of them, and what does each do? Are they wired in series?

Reason for question: on my 82SC, my brake lights seemed to have stopped working, so I was going to replace the switches ...bought em online and popped the hood to go at it. Then saw that one of the connectors had simply fallen off the switch and was just laying there ...or at least I think had fallen out? Or was it left off intentionally by the prev owner like 15 yrs ago?? So I did the sensible thing: plugged it back into the switch terminals. Tried the brakes and wha la!! ...brake lights work now! Thinking I'm done, I button it all back up. Then I drive the next day and now my dashboard brake light switch is permanently on!! Huhhh??? So what the heck is going on here, guys? Anyone got any answers for me here? Is it possible I only needed one of the two switches hooked up and that one switch failed? But then why are there two if that were the case? Call me confused! What do you guys think is going on here??

Edward

wareaglescott

I am not n expert on it but those switches are wired in series I believe and also work together with the parking brake light. The dash light has more meanings than just the parking brake handle is pulled. I believe it can also warn of system failure. Hopefully someone can come along and explain the system better.

Bill Verburg

Edward

Thanks for that, Bill!

Pardon the lame 2nd question, but does "each brake circuit" in the schematic mean one switch is for the front and one for the rear brakes?

Edward

Bill Verburg

yes

Bill Verburg

Here's a cross section of a 930 m/c, 911 is the same just smaller bores. There are 2 pistons(#8 & #9) separated from each other. 1 for the front and 1 for the rear

Edward

Outstanding, Bill. Big thanks for that, sir ...very much appreciated!!

Edward