Handbrake Warning Light Switch

[Rosco_NZ]

I need to replace the handbrake switch which drives the warning light in the dash.

The switch in my ‘72 911T has 2 terminals, one comes from ground side of the light, the other to ground. When the handbrake is activated, the switch completed the circuit to ground, light goes on.

The pet number in the PET is 901 613 521 00. All
pictures of this part show a single spade terminal only. Does the mount screw on this new part earth the connection? Or do I need a different part ? Without a ground connection, I can’t see how to make this single connection switch work ..

[Dpmulvan]

Originally Posted by Rosco_NZ

I need to replace the handbrake switch which drives the warning light in the dash.

The switch in my ‘72 911T has 2 terminals, one comes from ground side of the light, the other to ground. When the handbrake is activated, the switch completed the circuit to ground, light goes on.

The pet number in the PET is 901 613 521 00. All
pictures of this part show a single spade terminal only. Does the mount screw on this new part earth the connection? Or do I need a different part ? Without a ground connection, I can’t see how to make this single connection switch work ..

US only cars had two terminals, the switch your talking about goes to the Master cylinder. Just piggyback the two wires.

[HarryD]

Are you sure it is the handbrake switch and not the switch which is wired in parallel on the Master Cylinder. To verify, pull the wires off of the MC and see if the handbrake switch functions properly.

[Dpmulvan]

The switch is in the master cylinder, not the handbrake.

[HarryD]

Originally Posted by Dpmulvan

The switch is in the master cylinder, not the handbrake.

There are two switches. One on the handbrake and, for USA cars one on the MC.

[Dpmulvan]

Originally Posted by HarryD

There are two switches. One on the handbrake and, for USA cars one on the MC.

Yes I know, but I don’t think the OP does.

[HarryD]

Originally Posted by Dpmulvan

Yes I know, but I don’t think the OP does.

Agreed. The two switches are in parallel.

[EC900]

If Rosco NZ removed his parking brake handle and found a two-prong switch underneath - might it be the wrong one was installed…(?) based on that part number he supplied.

Does he mean the Brake Pedal switch (?) this has two terminals as well as the MC fluid pressure activated switch… or does he mean the actual red “Brake” dash light indicator assembly. I don’t know if the 72 has it on the dash or in the speedo, but the switch inside the handbrake is a single terminal.
Also, he doesn’t mention his symptoms if the light is intermittent, constantly on or not operating at all, nor the wiring involved where he’s looking.

The handbrake switch # he refers to on his PET is the correct one for just the handbrake handle - with one terminal and should be connected to a single brown/yellow wire that routes to the red dash indicator light. So one has to wonder what he’s looking at and referring to. It also could be the Contact Bow (which grounds on the handle and not the single adjustment/mounting screw on the side) might be broken too or out of adjustment which will affect the dash light always staying off or on. Broken contact bow will keep dash light off.

I went through this dilemma and when I tried to adjust an intermittent hand parking switch light (901-613-521-00) coming on, the riveted contact bow finally gave way and snapped, dash light stays off now whether handbrake is up or down.

Best if Rosco NZ can post pictures of what he removed and some symptoms for clarification.

[Dpmulvan]

Originally Posted by EC900

If Rosco NZ removed his parking brake handle and found a two-prong switch underneath - might it be the wrong one was installed…(?) based on that part number he supplied.

Does he mean the Brake Pedal switch (?) this has two terminals as well as the MC fluid pressure activated switch… or does he mean the actual red “Brake” dash light indicator assembly. I don’t know if the 72 has it on the dash or in the speedo, but the switch inside the handbrake is a single terminal.
Also, he doesn’t mention his symptoms if the light is intermittent, constantly on or not operating at all, nor the wiring involved where he’s looking.

The handbrake switch # he refers to on his PET is the correct one for just the handbrake handle - with one terminal and should be connected to a single brown/yellow wire that routes to the red dash indicator light. So one has to wonder what he’s looking at and referring to. It also could be the Contact Bow (which grounds on the handle and not the single adjustment/mounting screw on the side) might be broken too or out of adjustment which will affect the dash light always staying off or on. Broken contact bow will keep dash light off.

I went through this dilemma and when I tried to adjust an intermittent hand parking switch light (901-613-521-00) coming on, the riveted contact bow finally gave way and snapped, dash light stays off now whether handbrake is up or down.

Best if Rosco NZ can post pictures of what he removed and some symptoms for clarification.

US cars only had a two terminal handbrake contact switch in 72. They’re NLA and not needed anyway.

[thetorch]

Just went through this on a buddy's 73. Every version of the replacement switche seem to have a single pole, but his clearly has 2 poles.

Searching around I found this, which shows the 2 pin connector.

https://forums.pelicanparts.com/porsche-911-technical-forum/644361-hand-brake-cable-connection-e-brake.html

Then I found this wiring diagram, showing that the red dash light is also triggered by the seat belt warning.

https://forums.pelicanparts.com/porsche-911-technical-forum/817868-where-hand-brake-switch.html#post8133574

So it appears the light will go on with either, if I am reading that right. The connector at the switch seems to be a super ugly dual prong copper piece that I had a devil of a time trying to reconnect in situ.

Probably no one wants the seat belt warning anyway so folks rewire it to the brake only?
Happy to be wrong on this one, but seems like the only explanation I could determine.

[Rosco_NZ]

Thanks all for reply’s .. appreciated. For clarification, I am definitely referring to the handbrake / e-brake switch at the rear of the handle .. mounted via with a machine screw. It is in parallel with the master cylinder switch.. either switch grounding should bring on the flashing warning light. There are definately 2 terminals .. but seems they are or either side of the switch as I was thinking .. just a way of looping another circuit off the same point. The wiring diagram shows it looping off to the seatbelt warning light in the dash, which is not used. So I think that circuit is redundant anyhow.

What I was confused about was thinking the 2 terminals were either side of the switch, but now I think the device is not actually a switch but a receiver of a swiper mechanism, which makes connection to ground through the copper terminal on the wiper. So the single wiper part should work. Begs the question why 2 part blades were necessary and why it was not made this way in the first place …??