Mechanical Brake Light Switch Modification - '78 SC

[Craig_D]

Hi guys,
I got tired of worrying about my hydraulic brake light switch not triggering my brake lights early enough to pry the tailgating commuter's eyes from their most recent text and decided to get modern.

So, here's my mechanical brake light switch installation... one of my latest modifications to bring my '78 SC up to current safety and performance specs.

I started by purchasing a Beck/Arnley 201-1450 Brake Light Switch off of ebay for $8.92 brand new, because it has the adjustable threads to offset the trigger from the mechanical linkage in front of the 911 master cylinder.

Then sourced my garage for some new extruded aluminum for the bracket, a few plugs, some solder and wire, and here's how I did it:

[Craig_D]

With the bracket set up for the MC housing, I set out to mount it.





Test fitting of switch:


Now to make the wires with plugs:



Blade plugs for the ends:


Now what I did was test which two of the three plugs in the stock hydraulic actuator needed to be "jumped" by my mechanical switch, and then just stick the blade plugs into the back of that housing. This way, I have an hydraulic backup, in case the mechanical switch fails.

Here's the near-final test install (all I need to do to finish it, is install a plastic wire wrap to protect the wires):



The result is that my LED brake light bulbs are instant ON. The second I press on the brake pedal, my brake lights are on, so no more worrying about my hydraulic brake switch not activating the brake lights when I'm lightly pressing the brakes...such as I do in my morning commute often!

Cheers,

- Craig_D

[Craig_D]

Forgot to place the picture of me tapping the bracket. I forgot to also take a picture when I tapped the aluminum holes on the MC housing, but that's what I did for the two allen bolts to screw into.




The peace of mind I get from this modification, and the fact that it all cost less that $15 dollars makes it one of my favorite mods!

Cheers,

- Craig_D

[Smoove1010]

As usual, nice write-up, great pictures! The forum moderator ought to take your posts and use them for this:
http://forums.pelicanparts.com/porsche-911-technical-forum/770526-wanted-automotive-writer-create-diy-articles-pelican-parts.html

What's next on your to-do list?
GK

[Craig_D]

Ha! Thanks Smoove!

I have a few winter projects to do:
- sunroof seals and new cables
- Pedal assembly refurbish with bronze bushings
- Updating to Carrera window regulators
- Install new heater/vent control wires and finish AC removal dash hose routing
- Lightweight stereo (improve what I have by adding to my system but keeping it light)
- Removal of un-needed A/C and cruise control wiring (and stalk)
- Removal of power antenna
- Install light weight bumpers and crush tubes
- Install LED gauge lighting

Plenty to keep me busy!

[4flyboy]

Glued and subscribed.....thank you for the superb write up. Mad skills.....signed Envious!

[manbridge 74]

Nice work.

Another option would be to find a mechanical switch off any old German hulk awaiting melt down at the local pull-a-part and add it to the pedal cluster effectively backdating to earlier 911 design.

Speaking of pedal clusters, the 73 and earlier had the the forged clutch pedal (vs stamped steel) designed to be screwed in and out for setting pedal height. Just an FYI.

[Arne2]

I did much the same, but used a Hyundai switch instead, since the terminals cam out the side instead of straight forward. 2005 Hyundai Sonata 4 cyl. w/o cruise was the fitment, actually fits many Hyundai and Kia models.

[will hung]

This is very clever. Thank you Craig. Yet another project to add to the list.

[RWebb]

Originally Posted by manbridge 74

the 73 and earlier had the the forged clutch pedal (vs stamped steel) designed to be screwed in and out for setting pedal height

eh??

forged?

-------------

the right angled switch is a good idea BTW - easy for the PO to change after the adapter is made

[Craig_D]

I'm guessing he meant cast..

I was wondering about that though, because in my research I noticed some pedal assemblies had a location for a switch.

[manbridge 74]

Originally Posted by RWebb

eh??

forged?

-------------

the right angled switch is a good idea BTW - easy for the PO to change after the adapter is made

Cast

[Craig_D]

Jeff, I knew what you meant.

Any pics of one setup with a mech switch?

[Chuck.H]

This mech switch on the brake booster housing is a great mod, one of the best I've done though mine is not as clean as this install. You can check your lights are working at stoplights when you have a huge chrome bumpered F350 behind you to reflect in.

Chuck.H
'89 TurboLookTarga, 364k miles

[manbridge 74]

[KTL]

The 78-89 style of pedal & master cylinder setup like Craig has pictured here also has screw-ability for setting pedal height. It's the pushrod underneath the floorboard that goes from the brake pedal up thru the floor. The shiny plated one with the rod end on the pedal fulcrum and the clevis & pin up top to connect with the booster lever.

[morrisjm1]

Nice!! I've wanted to do something like that, but my small brain wanted to rig something up on the pedal cluster. Every time I thought about crawling under the dash to remove the pedal cluster, I quickly thought of something else to do.

Thank you,
Mike

[g150driver]

Great thread. I wanted to chime in with my take. I was about to copy your method, but my inner anal-retentive didn't want to drill into the housing. So I was looking at ways to use existing holes, and on a whim decided to try something using a grommet.

I used the same 2005 Hyundai Sonata BLS. I went poking through the pull-out bins at the local hardware store until I found a grommet that was just about the same diameter (little smaller) as the nylon plug that's normally installed on the front of that housing. Then I grabbed a couple extra M10X1.25 jam nuts and 10mm washers from the hardware store.

As luck would have it, the Hyundai BLS barely fit through the center bore of the grommet.

I had to trim the grommet down a few times. Pictures speak volumes here:



Here you can see the grommet, it just perfectly slid in.



I had to trim it down several times. The hardware store only had one, so I took it down in small slices. As you can see, I took off about half of the small diameter section.






Here's the final product. Looks like a "normally open" drain plug! Just insert and tighten with the nut adjacent to the terminal end of the switch.





I may go back and look for a slightly larger diameter washer, but aside from that I'm quite happy with the outcome. It's in there quite firmly.

Added note, if you have someone there to hold down the brake pedal while you're inserting the switch and tightening down the compression nut that would help. I used "The Club" against my brake pedal and steering wheel.

Cheers!

-Gavin

[dan88911]

Hey that is a nice setup g150driver.
Were are the opposite ends of the black and red wires attached?
Are you by passing or slicing the original setup?

[g150driver]

Hey that is a nice setup g150driver.

Were are the opposite ends of the black and red wires attached?

Are you by passing or slicing the original setup?

Well, funny you should ask. For now I have male blade connectors plugged into the green/blue and black/yellow terminals of the OEM plug for the forward pressure switch. I have an '81 SC, so I have three-prong switch. And the inconsistency of the new switch has caused my brake warning light to come on, so that should be fun to sort out! I'm afraid new pressure switches and a diode may be involved in the solution.

But if you're lucky enough to just have two-prong switches, I'd recommend just unplugging the forward plug and plugging your new switch into that. Or if you're feeling frisky, you could use some piggy back connectors on the blades of the pressure switch to hook in the new mechanical switch and make a short harness to jumper to the OEM plug. Then you'll keep it original, have triple redundancy, and retain the ability to undo everything in about 10 minutes.