brake light switich

[Van Miller]

356 Talk;
I know this has been covered, I have just reviewed recent posts; but is there a switch that will hold up to silicone brake fluid better than others in 2011? I have 2 disc brake cars with silicone brake fluid, the Master Cylinders have been good for 20 + years on both but switch life is so variable. One car had Porsche switch, it was good for years then quit. Other care went through mulitple Porsche replacement switches, sometimes in a few months, sometimes in a year. It seemed like I was doing better with the Harley Davidson switch, (about half the price of Porsche part from various venders), but now those are only lasting a couple of months. The switches are easy to replace, but any one know of the best bang for the buck?
Van Miller
64 C and 57 Speedster with disc brake conversion

[Kevin Wills]

I installed a motorcycle style contact switch at the brake pedal on the 62. My ATE switch quit working unless I pushed REALLY hard, so I got a replacement which leaked. I bought another replacement and the crimping where the wires hooked up failed. It nearly blew the top right off. After two failures, I put the ATE switch back on and put the switch on the pedal. 9 months later, it still works perfectly. Its not original, but it works for me...

[Wil Mittelbach]

Van -
This is probably of little help/consolation.
However, I've also changed to silicone brake fluid in my `65C cab with its original 46yr-old brake light switch, which still works flawlessly - - so far!
Determining your switches failure mode would be of interest.
- Wil
Huntington Bch
(formerly MB).

[John Hearn]

I have had three new brake light switches on my '59 coupe (which has silicone fluid) installed in the last fifteen years. I have taken apart all the replacement switches after they had failed. I every case the failure was dirty contacts due to arching or the modern "soft" plastic had melted and covered the contact with an layer of non electrical conducting plastic. My theory is that the original switches were made from a harder different type of "plastic". 6 volt was the norm for 356's back then. The replacement switches we are being offered today are I believe for 12 volts, which means the current capability is half that than for 6 volts. They are also usually made in Brasil (if VW) or another third World country! I also don't think they are tested to a realistic current drain level with any amount of reserve. In the good o'le days components were tested to at least a 100% overload safety factor.
My current brake light switch installed this June is from an East German Trabant car. As things never changed in the days of Communism I are hoping the switch will be the same specification as the originals installed in Stuttgart. Trabant cars were also 6 volt for many years, I am reasonably sure they did not de-rate the switch with the change to 12 volts.
KTF
John

[Vic Skirmants]

Well, let's try this again. I must have sent my post at the same time as John's, so mine seems to not have arrived.
Per Neil Goldberg, who got the recommendation from Chuck Stoddard, the NAPA brake light switch, SL144 works well with silicone brake fluid. It has screw-type terminals.
Also, a warning to NEVER use silicone brake fluid in a race car!

[C J Murray]

Also, a warning to NEVER use silicone brake fluid in a race car!

I wouldn't use that crap in anything!

That should liven up the thread.

[Dave Overington]

Apparently not. Seems to have killed it

(Ornery ole' DOT4 brake fluid seems to work perfectly well on my cars - not sure why others are opting for a "new and improved" troublesome option)

[John Hearn]

OK I will take the bait!
NEVER use Silcone brake fluid in anything?
Why?
We have been using silcone brake fluid since Mike Smith bought a pressure brake bleeder from the former Formula one Toleman team when they sold up.
If it is good for F1 why not a 356?
Does not attract water, has a higher boiling point, does not attack paint and so on.
As long as it is correctly installed (slowly) it beats regular fluid hands down.
We even use it on our race cars...........
The reason that I have taken apart my dead brake switches is to try and understand the cause and to end the "myth" that they are damaged my the use of silicone. My findings are that the mechanical side of a brake light switch which is in contact with fluid are working as should be on a dead switch. It is the electrical contacts that fail and the are surround by air.
KTF
John
PS Formula 1 are the guys that turn left and RIGHT if you didn't know!

[Van Miller]

Forum guys
Thanks for responses on my question on brake switch failure. Particularly thanks to Vic Skirmants for recommendation of Napa part. Also I enjoyed John Hearns thoughts on why 12 V switches may not be as tough as old switch. That stuff we learned in high school (Ohm's Law I think), comes in to use every so often. I find it hilarious that I may go looking for a Trabant part. My family just came back from summer vacation to Germany/Berlin and the Trabant is a featured joke. They are on display - can be rented. The Trabant encapsulates everything that was wrong with the old Soviet system. I guess it has become cool to have one of the worse cars ever made.
Van Miller

[John Clarke]

Hi Van,

Regarding Kevin's "Fix" It probably works superbly, but if the original Pressure Switch is Not used, Then remove it and install a plug. These Pressure switches can break down with age and can Suddenly Fail ! Disasterous, especially if You are still using the original type of Single Circuit Master Cylinder !
Let's now join the debate, Reference the Brake Fluid. We have always used Dot 5 Silicone Brake fluid in the 356 with No Problems Whatsoever. Hardly ever requires topping up, No corrosion, or Boiling.
Interestingly though, We Can't use the Silicone Fluid in Our Old Bristol 2 Litre. This has 4 Pot Disc Brake Calipers fitted at the Front as an upgrade and with the Silicone the Pads can Bind On as the fluid doesn't return so quickly to the Master Cylinder! Doesn't happen with the Dot 4 !
Anyway, Won't be changing the 356 System. Sorry to sabotage Your Posting.

Kind regards

Jay

[Wil Mittelbach]

John -
Your quite right.
Your switch failure investigation and analyses, and preference for silicone brake fluid is most informative.
My 6v original switch functions with silicone brake fluid as it previously did with DOT 3/4 fluids, changed after their severe adverse effects on my brake hoses, m/c and paint. Conversely, to other opinions, still have a relatively "hard" brake pedal with silicone fluid.
A local well known 356 restorer and racer has also switched to silicone brake fluid for his cars, particularly for those with intermittent usage to avoid corrosion, deterioration, and periodic bleeding with DOT3/4 - - he's had no brake switch problems.
- Wil

[C J Murray]

Just a few thoughts.

I had silicone fluid in my '67 911S for 15 years and replaced my brake light switch at least 8 times. Since returning to DOT4 10 years ago I have replaced 0(zero) brake light switches.

The S had great brakes before silicone and after silicone. With silicone it had a mushy pedal even though the system was totally rebuilt at the time of change and the system was bled multiple times.

Silicone is statistically more compressible than DOT4.

Silicone statistically offers less lubrication and causes the seals to drag with stiction as they move in the bore.

In the late '70s the motorcycle and performance car world went nuts for "space age" silicone brake fluid. The vehicle manufactures ignored the stuff and the aftermarket sold the stuff in large quantities until people finally realized that it had too many shortcomings and it fell out of favor with performance minded users. Harley Davidson is the only manufacturer that I know of that actually sold new vehicles with silicone installed. Their motorcycles have the reputation for having terrible brake performance but their customers are not concerned with performance. Harley customers are concerned with shiny paint and chrome. The silicone fluid does not attach the paint on your gas tank when the master cylinder springs a leak and that is why Harley uses(or did?) silicone.

I am not aware of any F1 or Moto GP team that uses silicone today. As far as I understand, the racing community used that crap for about 5 minutes, in the '70s, before they dropped it like a hot rock. I can't remember the details but back then a famous race driver was guest driving for a team that used silicone and after the first practice he demanded that the silicone be removed or he was going home.

No, the brakes on my 911 never failed in the 15 years that silicone was installed but it and the bikes that I had it in never functioned well. Use DOT4 and bleed the system every 2-3 years for the best brake performance.

[David Baugh]

Hi, Van.

I used DOT 5 in my 58 many years ago. After going thru a 6-pack of switches (they used to be about a buck from Whitney's), like you, I cut the failed ones apart to see what was going on. I didn't find the melted plastic that you mention, but every one of them had burned material on the contacts. I concluded that the tiny spark emitted upon contact was burning the silicone, and leaving a residue. I tried packing the switches with grease using a hypodermic needle, hoping to isolate the silicone from the contacts. That didn't work.

I finally rigged up a mechanical switch to the right of the brake pedal. I mounted the generic switch to a bracket that I attached to the accelator pedal bracket, and then fashioned an aluminum "trigger" that I attached to the brake pushrod. Also had to cut a notch in the wood floorboard. That solved all of my problems, and was barely visible under the accelerator pedal.

It wasn't the hassle of replacing the switch that concerned me. I just never knew when my brake lights would fail. Rear-ended 356's aren't pretty.

During my recent restoration, I replaced all components of the braking system, decided to go back to DOT 4 fluid, and removed the mechanical switch. Other than the switch failures, though, the silicone worked flawlessly for years.

Dave

[John Clarke]

Hi C.J. and David

Always open to persuasion. All very interesting this, because although I am a user of the Dot 5 Silicone Brake Fluid, I do always seem to have a problem with my brake lights. 2 things (the second One very strange)
First the brake lights only work after a very hard push on the Brake Pedal. We always have trouble when putting the 356 through its annual government test (MOT). And secondly when the Brake Switch/Lights Do operate, Our 6 Volt Electronic Rev Counter/ Tacho ( this is fitted cos We run a 912 Lump) flips right round the clock to 6000rpm and back again. This strange occurance is more pronounced in the Wet!
Spoke with Joe Leoni on this and He was as baffled as We are ! We do use the Dual Circuit MC.
Perhaps its time to replace the switch and monitor this. With a change back to Dot 4 if no improvement.
Also, Its interesting that the American Military have requested to stop using the Silicone!

Cheers

Jay

[Jim Liberty]

Vic you are one of my few heros. But I disagree about the silicone brake fluid. I've used it for as many years as it has been produced. That said, I do spill more than most guys.

..................................Jim.