I had my brake lights go out on me at WCR. A couple of members offered to help replace or the switch and now I am thinking I should have taken them up on the offer.
The problem is when I install the new switch it does not work. The switch is good mind you. I have tested it outside of the car and it switch current off and on. Wwhen I plug in the electrical connection with out mounting on pedal bracket, the switch works. It closes the circuit defaulting to ON when left free. Now when I go to mount the same switch to the bracket, the switch no longer works. It is not about how much the arm moves. as soon as the switch base touches the bracket the switch motion is meaningless. it just won't close the circuit for bright brake lights. What is causing the short? Is there supposed to be a separator between the switch and the bracket? Any suggestions at this point?
TIA

You have the arm on the driver's side of the disc yes? Setting up the switch P.129 section 30 in your Haynes. Fig 9.24 shows rhe correct orientation.

switch arm is on the drivers side of the washer. As I said in the initial description it is not about the action ofhte arm but the fact that when the assembly of the switch touches the bracket there is some sort of short that keep the switch from registering and open circuit to engage the brighter action of the brake light. IT's all good until I mount the switch to the bracket.

Going to the PCA-OCR concourse in Dana Pt. tomorrow, but if I can't clear this up I will leave the brake light in the default open position until I can figure it out next week or the brain trust here can provide some other alternatives.
The switch is a URO product from pelican . maybe I need to get the Porsche oem version instead and see if that is the issue. I cant understand why that is the case when everything is okay until it touches another metal surface.
Thanks,

Since the switch is normally closed and opens when the lever is pushed, your symptoms indicated that something about mounting the switch is causing the lever to move.
It might not be moving the lever directly but maybe distorting the switch body enough to open the contacts.

The original switch has an adjustment screw and I assume the URO switch does as well.
Try adjusting the switch. A DVOM help with adjusting.


Jim

Hold the switch in your hand, wires connected, ensure that it is working properly (as per your posts above). Now, whilst still holding it, connect a wire from the mounting point of the switch to whee it would mount on the pedal cluster. With that wire attached does the switch still work properly? If no, then the switch must - surely? - be faulty.

There is no separator/insulator since the switch should be isolated by virtue of the fact that the screw threads on the switch are just inserts pressed into the plastic and shouldn't be connected to any other metal in the switch. (I've used both the URO and the Wittrin brand switches, and both of them are built roughly the same, and are both adjustable.)

In terms of adjustment, is the washer on the pedal able to FULLY pull away from the switch while it's being depressed, as in there's a gap between the switch arm, and the washer? If the washer is still touching the switch arm at all, the brake lights won't come on. The brake switch only makes contact and closes the circuit when it reaches the absolute end of stroke, which is set using the locknut/screw on the switch, I have mine adjusted so that the washer pulls away from the switch arm and actuates the lights just the tiniest bit before I start to feel any resistance from the brake pedal.

With the switch mounted but no wires connected, are you able to get continuity between the terminals when you push the pedal?

(And, if you're concerned about a short, with the wires disconnected and the switch mounted, are you able to get continuity between either terminal and the vehicle chassis ground?)

If you have the wires connected (should be one with a bundle of ...I think 3 wires that provides power into the switch as well as teeing off to your reverse lights and another circuit, and another single wire that actually goes to your brake lights) do you see 12v on one side and ground on the other with the brake pedal at rest, and then do you see 12v on BOTH sides with the pedal pushed down?

Thanks for the info and reply. I am now going to have track down more issues as result. Yesterday while driving Generator light stayed on while driving. then wound up losing all gauge electrical, tach response, no brake light on the combo gauge with the e-brake pulled up. No it is time to go back and start checking fuses and relays to see if was just a part heading down hill and the first sign was the brake lights not working. Also was not get good throttle response on the drive back while the red Gen light was on but getting dimmer??? Ahh, the joys of old car ownership.

Well let's see... The generator light is fed power through fuse 9 to the light and then to the regulator on the board in the engine bay, fuse 9 also feeds the gauge indicator lights, several gauges themselves (including the tachometer), the brake lights, AND the brake warning lamp on the gas gauge (through the emergency flasher unit's, which is powered through the emergency flasher switch) Edit: "through the flasher relay, which is powered from the emergency flasher switch"

If fuse 9 is blown, making bad contact in the holder, or the wires plugging into it on the back of the fuse panel are corroded and not making great contact, that would affect the gauges, brake lights, and the brake indicator, and make the generator light behave wonky.

And that's just the protected side of fuse 9!

As far as throttle response, the supply side of fuse 9 branches off and goes back to the relay board and feeds 3 things: Coil power for the "Power Supply" relay, coil power for the Heater Fan relay, and terminal #15 on the ignition coil.

Eesh...Fuse 9 is really important.

Love the info. Thank you so much. Time to check fuses or lack there of. I may have bumped one or two with my head being under the dash working on the switch. The plastic cover plate has been gone, not lost, for a couple of years now. Need to gather up some replacement fuses first and see what is going on. Better yet, I have been meaning to replace the fuse box with a Jwest fuse box instead.
This is what I love about this site. The wealth of specific knowledge is better than any manual available. Options, shortcuts and true experience in every aspect an permutation you can think of.

I end up learning more and more about my own car while I'm offering help to others, as far as I'm concerned it's win-win! Even if my suggestions turn up dead wrong, it's still fun to brainstorm over the possible cause.

I ended up getting the Jwest fusebox a little while back because of how corroded and damaged my fusebox had become... and getting tired of picking fuses up off the ground every few weeks when my shoe brushed against it. It's a very good investment, and if you replace the fuses with ATO circuit breakers, you don't have to worry about being caught in the situation where you're in the middle of nowhere, accidentally short something out, and have no fuses left. Just reach down and push the button back in. (Or you can really splurge and get the self-resetting type. I went with manual-reset. Slightly more work, but it just felt safer.)

Bad fuse, fixed that and reinstalled the switch and it came back to life.

3 months later to the day, there's the successful payoff! Glad to hear it's fixed!

So am I. It didn't take 3 months to solve though. I'm really happy that people behind me see I am braking.
All electronics are back up and working.
I posted because I realized I hadn't closed the thread.

Just happened to me today, read this and I’m back in action

Trip down memory lane reading through this thread again!

Hey, guys! I had a brake light problem and although I suspected that the cause of it was an upgrade I had done at a local shop, replacing the stock 17mm master cylinder to the beefier 911/914-6 19mm unit, I was reluctant to assume the contortionist posture and plunge into the car's footwell guts myself to adjust that brake light switch. However, I finally did just that and using the previously cited HAYNES 9-24 procedure, along with a careful review of the material on this here, I successfully got my brake lights back operating as normal!

At this point, I'd normally say "This Bud's for all of you who illuminated this problem for me" but given the recent rather unfortunate advertising Budweiser caused such a kerfuffle over, I'll simply say (in the best German Oktoberfest manner), "Prosit und Vielen Dank!" My car ('Jezibel') is greatly relieved to be letting all those nasty Semi-truck & trailers out there on the road know whenever I am slowing down or stopping! Nothing worse than a Mack-Truck enema, after all, when you're only 48 inches off the ground!