I laid my wiring harness back in the car last weekend and have a question about the brown and brown/white white that leaves the main wiring harness just after the firewall in the front trunk.

What does it terminate to? It continues down to the brake master cylinder pressure fail switch. I know what to do with it there - but what does it attach to up top?

I am working on a early '72 model year.

Thanks in advance!

Looks like the brown/white goes from the brake warning switch (32) to the upper left light on the gauge.

EDIT: Bollocks. I don't know what i'm talking about ...

Thanks Andy,

I have the brown white in the guage cluste attached to the warning lamp. This is in the front trunk (barely). Maybe switch 34 is the clue - let me grab my book - I have been working off a laminated schematic and there may be ommissions.

Picture:

Click to view attachment

Hmmm - 34 is handbrake contact - still confused.

Lemme go look.
From what I recall, the old switch on the master had two prongs...the replacement has one prong.

Give me a minute.

Rich

Rich,

This wire continues down to the MC location through the body with a grommett and then to the wires with the boot. The wires in question are between the MC and the firewall entrance.

The way its hooked up now is right.
I have one wire not doing anything due to the new sensor.

RIch

Thanks Rich,

These wires would never reach the MC sensor - and the wires at the MC have two wires (Brown = Ground and Brown/White = Warning Lamp).

MC sensor wires:

Click to view attachment

What angle is that picture at? I believe the grommet in that picture is one I was trying to identify in my grommet thread.

Hi Bruce

The picture was taken from below where the MC would be.

lemme go look at the breakout where you show it.

rich

1. Can you double-check the colors? From the picture it seems that none of the wires is white.

2. Are you sure you routed the wires the right way? It looks like the buzzer and door open switch would connect to that white and brown wires but that's located under the dash.

not much help here.

71 does not have that breakout in the harness.
early 72 has the breakout but its blowing in the wind...not plugged into anything.
saying that...my fresh air blower on the 72 has never worked...

Rich

I've seen brake fluid reservoir caps that had two terminals on them, maybe your harness was modified to take one of those. It's the right length, and wired to the correct wires...

Hmmm, that does look odd there. Ignore my previous post, i was thinking of a different wire.


This main harness does not have that brake-out connection:

That is funny.
I love how everything looks easy enough to find....till you get to the pile of wires marked "gauge cluster"

Rich

I checked a 72,73,and 74. The 73 and 74 did not have the upper wiring. My 72 ( ) has the upper wires but they are not plugged into anything. It reminds me of my BMW 2002. The brake cap is the same style but has a float attached to the under side. Two wires plugged into the cap and activated a brake light warning if the fluid level was low. I don't think you need to worry about those Mike.

The lower wires are for the brake light switch on the master cylinder. If the wires don't reach the switch location check to see if you have it run correctly on the other side of the firewall. You may have a snag caausing the wires to be too short.

I have owned this car since 1978 - unmolested - I'm the second owner. This a factory wiring harness - no mods.

Maybe the factory was going to use the fluid reservoir with a pressure switch cap (perfect length) buy chose not to later?

Odd to leave the wires there unterminated - slight potential for a ground.

Wierd........

I looked at Abel's wrecked 73 and I dont see a break out...it may be under the tank, but I cant see it there.
Cap was from a box of parts...so that wont be OEM...


Rich

There's a grommet thread?? I need to find that!

Hi Valy,

Thanks for the reply.

Here is a picture (definitley BRN/WHT). These wires are for sure located in the right spot as the grommet for the main harness that goes through the firewall was never removed so these are on the correct side of the firewall.

Click to view attachment

It wasnt an official thread, but heres my grommet thread.

http://www.914world.com/bbs2/index.php?showtopic=126367


Does anyone know if the master cylinder switch boot is the same as the backup light switch, and the 3 port fuel pump connector? Sorry for the hijack

Thanks for the link Bruce - not a hijack from my eyes - I need to know as well

Cheers!

Yep. same-same.


Nope...its different.

The Brown/White at this location and the Brown/White at the MC are wired in parallel making me think that this was indeed wired (from the factory) for a pressure cap at the fluid reservoir. If either switch closed then the warning lamp would come on.

Interesting!


You should probably tape those off ...

I will tape them off - but I wll also bring them up near the top of the fluid reservoir cap (or to a place I can grab them) just in case we discover more about this oddity in the future.

Thanks for all your help - I thought I had lost my mind - cheers!

Interesting thread. Looks like 1972 only wiring to the brake reservoir cap that Porsche never used. Mike, the BMW 2002 used the same screw on cap but had two male terminals for wiring. I wonder if Porsche planned on using the same cap but never installed it for some reason or.... maybe it was ROW thing... strange.

Ive seen many caps in Pick A Parts that have terminals on them and look like they will fit. I will grab one or two for anyone with a 72 interested in hooking one up and sees what happens!?

When I was working on my daughters 1972 I encountered the same wires.
I assumed that the wiring harness was from a different year 914. I just put on shrink tube to isolate and then ignored them. Interesting to find out after all this time.

On German wiring systems the Brown/White is always a grounded switch connection. Ground the wire and see what activates. It is part of the brake warning circuit. Most likely the brake indicator will flash when grounded. The solid brown would be the ground source for the switch. I have similar wires connected to my MC through a hole under the tank.

Bruce,

If you have seen that cap on 914s it might validate the thoughts here. I would like to incorporate that feature - why not it is wired for it.

Cheers!

It will be a month or three before I am ready to power up the car - but it is wired in parallel with the Brown/White at the MC so it will activate the same warning lamp in the guage.

I found this image searching on the BMW 2002 reservoir cap number 34 32 6 756 226. It is a $30 part new.

Bruce - does this look like what you have seen in the Pick-A-Part yards? If a 914 ever shipped from the factory this way I would like to have the right cap. This car is going to be a 90+ point Concours - maybe I will get another point??

Click to view attachment

This one is just the same as mine, but along with the optional wiper intermitent relay wire, they were taped back into the harness. I would put one on if you found a cap BD. There are such caps for later air cooled 911s. Think they would fit?

Now to wander. I am trying to figure out what the diodes wired into the brake light warning circuit do. They are attached at what I am pretty sure are lights at the back of the fuel gauge. Normally I can figure these out, but the 72 wiring seems unique and the diagram is tough reading.

Fractured a vertebrae pulling the cord on the snowblower so it is light chores till the heat blows over. No, it DID NOT start.

Mike, do you have an early 1972 or late? What are the last 5 of your VIN? I am collecting data on the chassis harnesses and would like to look into this issue further. First I have heard about it.