Where is the brake light switch on a 73 911

[yelcab1]

This is a picture of the pedal cluster on a 1973 911 chassis. Where is the brake light switch ?

[john walker's workshop]

On the pedal assembly.

[john walker's workshop]

That's a power brake setup, not 73. On the master cylinder on that setup.

[proporsche]

looks like hydraulic clutch as well on the pic....
here is a link to guide you to your switch
How I adjusted the mechanical brake light switch on '74 - 911

[Walt Fricke]

Where is the master cylinder? Up under the hood by the cowl? If so, it has been converted, either to have power brakes (does the MC have the big pie plate diaphragm vacuum reservoir between the driver and the MC?), or simply to the location where the power setup was moved (one could dispense with the vacuum power part easily enough). This overhead setup has the brake light switch integrated into the MC.

Earlier cars (the power brakes came in at the end of the 1977 model production run for non-Turbos anyway - early ones like mine had some of the infrastructure, but not the power braking stuff) had the MC located on the firewall just in front of the pedal cluster.

If I read the parts catalog, the 72-3 911s had a switch screwed into the MC which closed when the brake pedal raised the hydraulic pressure.

Even earlier models had an actual switch where John has it - on the pedal cluster, which was closed by the movement of the brake pedal itself. As I recall it had two wires connecting to it (a typical NO switch), so easy to find looking around at the cluster.

Otherwise, look for the wires leading to the MC, wherever it is. Be aware that at some point (by 72?) a switch was added to the MC to light a dash warning light if you didn't have pressure in the brake system (fluid lost).

I've often wondered if it would be worth it to retrofit a power brake setup with a brake pedal actuated switch. The hydraulic MC switches seem to fail more easily than mechanical switches. After all, they are subject to significant pressure, and if not properly made, can leak into the electrical side of their diaphragm. Happened to me, though the FLAPS replacements have held up well.

[yelcab1]

Yes, it's a 73 converted to a 993 variocam engine, with G50 gearbox, and vacuum assisted brakes. I found the 3 pole brake switch screwed to the side of the master cylinder. Need to get one of those.

[HarryD]

Originally Posted by Walt Fricke

Where is the master cylinder? Up under the hood by the cowl? If so, it has been converted, either to have power brakes (does the MC have the big pie plate diaphragm vacuum reservoir between the driver and the MC?), or simply to the location where the power setup was moved (one could dispense with the vacuum power part easily enough). This overhead setup has the brake light switch integrated into the MC.

Earlier cars (the power brakes came in at the end of the 1977 model production run for non-Turbos anyway - early ones like mine had some of the infrastructure, but not the power braking stuff) had the MC located on the firewall just in front of the pedal cluster.

If I read the parts catalog, the 72-3 911s had a switch screwed into the MC which closed when the brake pedal raised the hydraulic pressure.

Even earlier models had an actual switch where John has it - on the pedal cluster, which was closed by the movement of the brake pedal itself. As I recall it had two wires connecting to it (a typical NO switch), so easy to find looking around at the cluster.

Otherwise, look for the wires leading to the MC, wherever it is. Be aware that at some point (by 72?) a switch was added to the MC to light a dash warning light if you didn't have pressure in the brake system (fluid lost).

I've often wondered if it would be worth it to retrofit a power brake setup with a brake pedal actuated switch. The hydraulic MC switches seem to fail more easily than mechanical switches. After all, they are subject to significant pressure, and if not properly made, can leak into the electrical side of their diaphragm. Happened to me, though the FLAPS replacements have held up well.

For my 1973.5, the brake light switch is a microswitch activated by the brake pedal in the footwell. The setup shown in the link from Proporsche shows my setup.

The only electrical connection on the MC is for the brake failure warning light.