Brake light switch and wiring

[tassie targa 76]

G,day all

I have added a vacuum booster to my 76 the booster is from an 84 so the pressure switch has moved from the previous maters cylinder place and attached to the booster in the trunk. Still using the existing 23 mm master cylinder and pressure switch

The car has been completely stripped down for resto and I'm now trying to work out the wiring. The diagram I have is. 76 USA and my car is a 76 ROW.

The m2 and m4 are stop and tail light but I cant see in the diagram where the switch wires in to send the signal to activate the stop or brake light I have a basic knowledge of auto elec but It looks to me as if they both come on when the headlight switch is activated.

Can someone tell me which component is the pressure switch in the master cylinder as shown in the schematic and how the system works.

Regards michael

[tassie targa 76]

The current switch is a 3 pin.


Is this part of the system

[ossiblue]

I don't have access to a mid-year diagram, but your second picture shows a mechanical brake light switch which was connected to the brake pedal cluster. In those cars, the pressure switch in the MC was for a warning light on the dash, not to activate the brake lights.

If you look at a schematic for a 78 or later, the pressure switch is on current track 50, for 82 or later, it's in part 3, page 1. Those are switches that activate the brake lights from the MC.

[timmy2]

M2 and M4 appear again at base line 50 and 51.
The notes after the description of the device annotate the 2 Base line locations for M2 17,50,and M4 13,51.
Device F is the switch.
The '78 drawing our host has will show the difference in wiring for the 2 switches at the same location and at Base line 88 for the brake warning device.

http://www.pelicanparts.com/911/911_Parts/911_electrical_diagrams.htm

Personally, I would just go with a single mechanical switch in your application. There have been some creative posts recently about doing just that.

[tassie targa 76]

This forum and it's members are the best

Dennis never fails to assist.

Both replays make sense and I now know how to go forward. Mechanical switch at pedal.

Regards Michael

[timmy2]

Michael.
Drop me an e-mail as I looked at your main thread and the thread about the whining CDI but no spark.
I can run you through the white coax wire arrangement to the 3 pin connector so you get it all oriented correctly.
I won't have time until late tomorrow or maybe the next evening as I am working all weekend.

Cheers,
Dennis

[tassie targa 76]

G,day Dennis thanks for the offer, but after more inspection there is a blown circuit that can be seen with the back off the unit.

I have a msd unit and coil on the way

My dad rigged an old coil and condenser from stuff in his shed and by passed the cd unit and the car started I guess that sorts out most things, like points, leads, power, timing ect.
So new unit should be here next week, takes a while to get stuff to Tassie from USA

But pretty sure we have it sorted now

Regards Michael