Brake Light Switch, Again?

[DRACO A5OG]

I just had a brain fart while reading the threads about this very annoying recurring failure issue even after replacing the two switches.

Has anyone attempted to use a low pressure Brake Switch manufactured by Painless Performance, TX?

I would think the pressure activated micro switch on the current OEM/Aftermarket part fails after it gives out over time and usage. In our case a very short time. I figured a low pressure switch would solve this issue since some of us have to put allot of pressure to activate the failing switch.

According to the manufacturer/vendors Low Pressure System works at 20-50 lbs. vs. 60-120 lbs. of pressure of the standard OEM/After Market systems.


I emailed their tech support for verification.

Found this link from a Volvo electronics expert. it confirms some of you recommending to go Mechanical, very detailed with a switch cut in half and animation of a Bosch system. It is his belief that it is faulty electrical design: http://www.sw-em.com/hydraulic%20brake%20light%20switches%20notes.htm

[911pcars]

The MC pressure switches aren't reliable nor adjustable. You can purchase adjustable pressure switches, but it'll cost x 2 with no guarantee of lifespan. I suggest going retro and install a mechanical switch acting on the brake pedal ala early 911s. Here's an early pedal assy. w/switch. Low tech is reliable as well as adjustable. Also it's easy to hook up a momentary switch to keep potential tailgaters guessing and at a distance. Should be fairly simple to fabricate a switch bracket.



Sherwood

[DRACO A5OG]

Well Poop!

They only come in 1/8" thread! I am this close to making them, (---) this close.

Anyone have any ideas?

Wayne, maybe you can encourage Painless Performance or Ron Wiring to manufacture for you?

[DRACO A5OG]

Update: I got the manufacturers to consider making low pressure for Pelicans via Pelican Parts.

Interesting note. One Manufacturer, the owner e-mailed me and stated besides the obvious malfunctioning MC, Leak, Fluid and Fuse/Relay, a TOO HIGH OF A LOAD on the switch could cause it to fail.

This makes sense because the Volvo Electrical Guru discovered the switches to have melted internally causing the switch to malfunction. Could this be possible, could the switch be getting surges or too high of amp load? If it did wouldn't the fuse/relay break?

Has anyone dissected a known failed switch?

Sorry for all the annoying questions, LOL

[DRACO A5OG]

Update:

The manufactuer contacted me and he is willing to make special metric version of his Low Pressure Brake Light Switch.

It runs on a 4 amps and he believes the two can handle the 8 amp load. To insure the switches will not burn out he also recommends a relay/regulator.

The minimum order would be 500-1000 units. Anyone interested?

Another thought I had was to install the OEM switch and attach a regulator on the 8 amp load to the switches, this should solve the swithes' premature burn out issue like this:




How do you guys feel about either solution.

Will do research on regulator/relay for the 8 amp load.

[cab83_750]

I tend to blow my switch almost one a year. Yes I am in pursuit of a more reliable switch. But based on the various thread, the mechanical conversion might be the best solution.

[911pcars]

Building a pressure switch to function reliably for a long period of time at a reasonable cost is a challenge when the line pressure can reach 2000 psi. Is it any wonder a $20 switch can endure these pressures for so long. A $75 industrial-quality switch should last much longer, if that's the direction you want to go.

Sherwood

[DRACO A5OG]

Thank you all for letting me rant like this

I re-read the Volvo Article and found that the Volvo Electronics Guru whole hardly endorses the "Mechanical Switch" conversion, in fact, he sells a kit for Volvo Owners.

I conceed it is possibly the final word in the Faulty Hydrolic Brake Light Switch.

However, he does endorse 2 possible fixes as an alternative to the mechanical switch mod:

...heat generating arc would be greatly diminished if a relay, with its milliamps of load current opposed to brake light filaments, were the actual load on the contact. ...so I would grant, that a relay might be a solution. I would suggest that a fly-back diode be placed across the coil in order to quench the inductive relay energy which would also cause contact arcing.

Another possible solution would be to convert the brake lights themselves over to LEDs, gaining the advantage of a marked decrease in load current being switched by the contacts

Please humor me to see if there is such a relay. I now have a good excuse to use LED's.

My plan is to switch to LEDs, Relay and then Low Pressure ( if I can have it made ) and post my findings. If this experiment fails, I Will submit to the Mechanical Switch with Full Encouragement.

However, here are my reservations on the Mechanical Switch Mod, maybe I am too negative and I hope I do not jinx anyone :
1. No Back Up Switch ( like the dual Hydro set up, I can still press a bit firmer to get the lights to switch on)
2. Possible failure of the bracket holding the M.S. and/or bolts ( since it is a mod, virbations and constant use may loosen the bracket and maybe the bolts. Yes, it can be lock tite but what about the bracket or make shift device we installed it to, we've seen them all)
3. Debris may interfere with M.S. (I don't know how many times I've dropped things near the pedal cluster i.e. flying cell phone, detached keys, Fries, The Damn Loose Carpet. I know brake lights are least of my worries at that point but it does happen)
4. Moisture may short switch out. (Guys, our P-cars Leak, I have a drip when I wash my car on the passenger side right at the location if it was on the driver side on my brake pedal, bzzzzt, no brake lights)
5. Adjustments Needed for M.S. it is bound to get sloppy or too sensitive.

This is why I am exhausting my efforts to solve this for our community and our loved one's Safety.

[gsmith660]

Originally Posted by 911pcars

The MC pressure switches aren't reliable nor adjustable. You can purchase adjustable pressure switches, but it'll cost x 2 with no guarantee of lifespan. I suggest going retro and install a mechanical switch acting on the brake pedal ala early 911s. Here's an early pedal assy. w/switch. Low tech is reliable as well as adjustable. Also it's easy to hook up a momentary switch to keep potential tailgaters guessing and at a distance. Should be fairly simple to fabricate a switch bracket.



Sherwood

I went this route also with a simple pin switch but I am retro fitting an early switch in for a more finished look. BTW good idea about the momentary isn't it amazing how people love to tailgate a Porsche just to get a better look.

[gsmith660]

Here is my solution to the brake light switch.

[drl911]

I converted to a mechanical switch on my '86 over two years ago and have never looked back....

Dan

[SXSMAN]

Originally Posted by DRACO A5OG

Update:

The manufactuer contacted me and he is willing to make special metric version of his Low Pressure Brake Light Switch.

It runs on a 4 amps and he believes the two can handle the 8 amp load. To insure the switches will not burn out he also recommends a relay/regulator.

The minimum order would be 500-1000 units. Anyone interested?

Another thought I had was to install the OEM switch and attach a regulator on the 8 amp load to the switches, this should solve the swithes' premature burn out issue like this:




How do you guys feel about either solution.

Will do research on regulator/relay for the 8 amp load.

I'm changing out my master cylinder for a larger one and was going to go with a pressure switch . I might be a player on the new switch . I will add a relay like many have done for their headlights . This should end the melt-down problem .

Good thread !

SxS

[911pcars]

Another spec to review when choosing a replacement hydraulic/electrical pressure switch is the pressure capacity of the switch; not the activation specs, but the hydraulic pressure capacity.

The aftermarket switches may be designed for low pressure systems (e.g. engine oil pressure) and not for the pressures encountered in a hydraulic brake system. Longevity may be an issue because of this. Not sure if there is a burst pressure issue.

My $.02
Sherwood

[scarceller]

I also have failed switches, my brake lights do not come on till I really get on the pedal. I just got my new switches in and decided to review the schematic of how the Brake light circuit works and I think I may now understand why they may be failing.

First, as already pointed out by DRACO they seem to fail because of arcing due to current load. The 2 bulbs most likely pull 5-8amps (Will measure this to be sure soon). You can see in DRACO's pictures that the right side contact is very pitted and damaged it looks like the result of arcing across that contact.

After a review of how they are wired they do in fact carry all the current to the lights across the 2 switches (meaning no relay is used).

Then to make matters worse they are wired on the 12V side of the circuit , meaning the switch cuts the 12volt side and the bulbs are wired to ground. From Electronics theory 101 I was taught this is a bad idea. It's always best to have a switch wired on the ground side if it is to carry any excessive load. Not sure of the physics here but the bottom line is that cutting the ground side reduces arcing across contacts. You often find most automotive switches (like the door pins and such wired to ground for this reason.

So before I jump the gun and go for a mechanical switch on the brake pedal I've decided to put 2 new switches in the Master Cyl along with a Normally Open 12V 30amp relay. I'm going to wire one side of the switches to ground then the other side to the relay coil. Then I'll apply 12V to the other side of the coil and simply have the switches ground the coil to activate the relay. The the relay main contacts will activate and apply the 12volts to the brake lights.

This will insure no more that 1/2 amp ever flows through the 2 switches and should keep them in good shape with very litttle or no arcing.

One other point about Incondencent bulbs is that when they first light up they draw at least 2 times momentary current than when they are fully lit. This means that these switches can see momentary current as high as 10amps or more when the switches first close.

One other idea would be to drive the brake lights not with a relay but rather with a PNP hi power transistor setup as a switch, sort of a solid state relay with no contacts. We use these types of circuits often in Electronics to drive motors or pick valves in Plant Floor Control (factory and manufacturing plants) where we can not tolerate any arcing because of flamable gases in the area.

[scarceller]

Here's a quick schematic for the idea in the prior post

[dshepp806]

scarseller: what did you install, as to the installed switches you mentioned?

Best,

[Formerly Steve Wilkinson]

I have one of the OEM mechanical switches that I've never gotten around to installing...need to fab a bracket first. Anybody know if there's an existing bracket for the switch that would fit an SC?

[DRACO A5OG]

Whoa, forgot about this thread.

I should have updated that low pressure BLS's is not the answer but the suppression of the arcing in the BLS is.

My company's BLS Arc Suppressor will correct this issue once and for all. PM me if anyone is interested. It does require you install two new BLS's, I ordered two new BLS's from our host.

[scarceller]

Draco,

Last night I installed 2 new BLS and added my own relay wired as shown in prior post. The relay works great but the switches still close a bit late but much better than the old ones. They don't require much force on the brake pedal to come on now but they still don't come on with very light press.

How much do you move your pedal before yours come on?

Since I now have a relay in place I can use a small micro switch on the pedal to pick the relay, I'm think about doing this, I think a very small micro switch should be easy to install.

Also, I cut my switch open and sure enough one of the internal contacts is really gouged from arcing. I think your solution for arc surpressing with a relay will solve this issue. Thanks for the work on this.

I will post some pics soon.

[scarceller]

Originally Posted by dshepp806

scarseller: what did you install, as to the installed switches you mentioned?

Best,

I bought 2 of these switches from here:
http://www.joetlc.com/brake-light-sw...o-p-16814.html
$5.00 each

They look a little diffrent than the stock ones, the stock are brass color these are silver but they fit just fine and seem to work OK.