Brake Light Switch, Again?

[NOLAsc]

I hope this reply lands in the right place...

Okay. Learned today that brake lights did not work (except for oh-S#*% situations when you really need to hit them) on my 82 SC. Went back to work and posted question the forum. Many pelicans came to the rescue, delivering knowledge I don't have. And Bentley on SC seems uncomfortably silent on the issue.

Now I have 4 questions:
1. Can anyone lead me through the steps for moving to a mechanical switch?
2. Scarceller offered excellent diagrams and photos for testing old and relay-protecting new switches, but I show 3 wires not 2 -- see diagram attached (?).
3. Could the issue be air in the system. My brakes feel fine, but I did open the system after buying the car a couple months ago. Changed out the pads and front rotors.
4. DRACO, are you still selling your relay?

[NOLAsc]

Sorry about the double diagrams. But I have a black wire, a blue&green wire and a black&yellow wire.

And I appreciate everyone's help.

[scarceller]

My 84 switches only have 2 wires. Did you actually look to see what the switches look like? Take a pic of your switches also if you can.

Kind of busy this week, but if I get a moment I'll review the schematics to your 82 car (I have these).

[scarceller]

Yup, your 82 switches have 3 wires:
gn/blk - 12 volt power
blk/yel - feed to brake lights
blk - this goes to parking brake light on dash

When brakes are not applied, the gn/blk is connected to the blk wire, simply power (12V) is sent to the park brake circuit.

When brakes are applied, the gn/blk is connected to the blk/yel wire, power is sent to brake lights.

Your switches are SinglePoleDoubleThrow (SPDT) switches. I'm not sure why in the 82 car they send 12V to the brake light circuit on the dash? My guess is that they do this to detect if one of the switches goes bad, I bet they light the brake light if a switch fails.

[NOLAsc]

Thanks Sal.

I didn't get a chance to read this response this morning and then left work with my Bentley's bookmarked to the schematic on my desk. Then I went straight to the garage after I got the kids to sleep tonight.

Anyway... My back-up Haynes manual seemed to show that, at least on the front switch, black/yellow switched between black and blue/green. I tested with ohmmeter to find that with one lead on black/yellow and the other on either black or blue/green the circuit remained closed when attached to the switch. I pulled the connector and jumped black/yellow and blue/green and the brake lights came on.

Don't know about the current to the dash. If there is supposed to be an indicator, that concept did not work - or something else failed. E-brake light lights when it is engaged and goes off when it is not.

Also, the lights come on when I brake. Just not under normal (for me) gradual city braking.

I really appreciate the advice I find here. I wish this forum was around when I had my 914s twenty years ago.

[NOLAsc]

Sal,
Would the relay circuit you developed work connected to the green/blue and black/yellow wires, leaving out the black wire that goes to the dash e-brake light? Here's the photo...

[NOLAsc]

QUOTE: "Don't know about the current to the dash. If there is supposed to be an indicator, that concept did not work - or something else failed. E-brake light lights when it is engaged and goes off when it is not."

REPLY: That was then. Now the brake light on the dash is on. Brake lights still work in harder braking situations. New switches should be here tomorrow or Thursday. Gotta figure out the relay set-up.

[zenith]

I've read all the thread and I am really thankful because I learned a lot about replacing my break light switch. I have one question though, when I went to order this parts online, I also see this stop light switch. Are these pertains to the same parts? thanks

[scarceller]

84-89 Carrera cars use 2 switches mounted directly on the master cyl. Search our host parts list for part # 113 945 515H - be aware that some cars had 3 pole switch but most had 2 pole. I suggest you check your current switch first to see if they are 2 or 3 pole/terminal switches.

Originally Posted by zenith

I've read all the thread and I am really thankful because I learned a lot about replacing my break light switch. I have one question though, when I went to order this parts online, I also see this stop light switch. Are these pertains to the same parts? thanks

[geoz]

Originally Posted by scarceller

Here are all the details and pictures for the new Brake Light switches and Relay install. First note that the stock wiring harness was kept as is and has not been altered in any way, so it's easy to go back to stock configuration.

Here's the schematic:


Here's a pic of the new switches and the relay along with the new wiring


Here's a closeup pic of how I wired into the existing harness, you can wire into any of the existing 2 connectors it does not matter which one you use. In the existing harness the Green wire is the power while the Yellow wire is what lights the brake lights:


This simple change will reduce the current through the new switches to less than 1/2 amp.

Brilliant post, love it. I just did this mod, my BLS almost arched out.

Thanks.

[jbm911]

I'm about to replace my brake light switches, anyone have a link to the relay in the photo in the previous post?
Thanks

[tazzieman]

Timely thread reactivation!
I hadn't realised just how much pressure is needed to activate these lights!
I'm sure my switches are original , but sounds like replacement might not be the solution.

Couple of days ago I found this thread SC mechanical brake light switch project and think this provides a belt and braces solution. What's not to like about this?

[scarceller]

Originally Posted by jbm911

I'm about to replace my brake light switches, anyone have a link to the relay in the photo in the previous post?
Thanks

It's a standard SPDT automotive Relay. They use these for Fog lights and alarms. Here's one on ebay 1 Pack Car Truck 12V 12 Volt DC 40A Relay & Socket SPDT 5P 5 Wire Replace | eBay.

Very simple install and works great, it really saves your switches from arching out.

[DRACO A5OG]

Sorry Fellas, stopped producing those BLSAS's. I do suggest getting OEM Brake Light Switches from the DEALER, they are better made then the aftermarket ones.

jim

[jbm911]

Sal - thanks for the info, that's what I was looking for.

Jim - I should have searched a little more before the PM I sent you, I saw in a later thread the arc suppressor had been discontinued.

Thanks for this great thread to both of you, very enlightening.

[Chuck.H]

For those interested in bypassing the pressure switches and using a mechanical switch, you can either put it on the pedal cluster, OR, you can remove the plastic plug on the end of the master cylinder support housing and put a switch there like I did.

This lets my brake lights come on with just a 1/4" movement in the brake pedal, WAY safer IMHO...



Sorry for the fuzzy pic, it's all I had.

Chuck.H
'89 TurboLookTarga, 335k miles

[911pcars]

Originally Posted by Chuck.H

For those interested in bypassing the pressure switches and using a mechanical switch, you can either put it on the pedal cluster, OR, you can remove the plastic plug on the end of the master cylinder support housing and put a switch there like I did.

This lets my brake lights come on with just a 1/4" movement in the brake pedal, WAY safer IMHO...



Sorry for the fuzzy pic, it's all I had.

Chuck.H
'89 TurboLookTarga, 335k miles

Because of the adjustment, I think that's a better option instead of the master cyl. pressure switch which doesn't have that capability.

BTW, even the early brake pedal mount switches have an adjustment limitation. The arrangement is such that adjusting the switch-ON contact also affects pedal engagement with the master cylinder. The arrangement/position of the washer on the link pin should be modified so it can be adjusted independently of the pin length.



Sherwood

[1984911p]

1984911p's Garage :: 1984 Porsche 911 Cabriolet