Parking brake warning blinking

[dicklague]

On my 1973 2.7 911. My hand brake warning light blinks continuously.

I guess it could be the hand brake switch adjustment, and I have not checked that out yet.

When I push hard on the brake pedal when the car is stopped the light will go out for a minute or so, but usually come back on.

What is in this circuit? I have studied the wiring diagram, but I have not found any ideas of what to trouble shoot.

Thanks in advance for your help and ideas.

[RSTarga]

push your handbrake down to see if it goes out.

[Jdub]

Fuzzy on this but it could easily be the master cylinder's brake switches (the ones activated by pressure via the brake pedal). I seem to recall they are wired iinto that circuit, but smarter minds will guide the way.

[FPB111]

Brake fluid level ok?

[RSTarga]

Yes it could also be a failing Master cylinder

[A horse with no name]

Originally Posted by RSTarga

push your handbrake down to see if it goes out.

+1...This has happen to me on the odd occasion.

[HarryD]

Dick:

I had the same problem a while back. When I removed the electrical connecter from the master cylinder the flashing went away except when I used the handbrake. You can access the switch by removing the left front wheel. Replaced the switch in the master cylinder and problem solved.

[dicklague]

Thanks for all your answers......I will start by checking the master and the switches.....that is what I was suspecting.

Will report on what I find.

[Dodge Man]

If not the MC. I have never seen a brake circuit warning light on my 73. There may be more than brake warnings on the flashing GEN/Brake light. Is it the top center light flashing? Low oil level is also tied into the flashing GEN light too. Kind of a catch all idiot light. A long time ago, I serviced a soldier's 73 MFI 911 brought back from Germany and it only had 3 quarts. A Porsche dry sump is worth every quart of the 10-12 at oil change. Best of luck.

[HarryD]

Originally Posted by Dodge Man

If not the MC. I have never seen a brake circuit warning light on my 73. There may be more than brake warnings on the flashing GEN/Brake light. Is it the top center light flashing? Low oil level is also tied into the flashing GEN light too. Kind of a catch all idiot light. A long time ago, I serviced a soldier's 73 MFI 911 brought back from Germany and it only had 3 quarts. A Porsche dry sump is worth every quart of the 10-12 at oil change. Best of luck.

If you check the wiring diagram (you can see them here: Pelican Parts - Porsche 911 Parts Listings & Diagrams), you will see that the brake indicator light has two inputs: The hand brake switch and the switch in the master cylinder. The oil level light is not part of this circuit.

[Dodge Man]

Originally Posted by HarryD

If you check the wiring diagram (you can see them here: Pelican Parts - Porsche 911 Parts Listings & Diagrams), you will see that the brake indicator light has two inputs: The hand brake switch and the switch in the master cylinder. The oil level light is not part of this circuit.

I have A VERY EARLY 73(9/72) and there are many earlier parts like cloth 356 rear brake line straps. Porsche never throws anything away. So wiring not to published spec may not surprising because there were lots of part year changes in the 72-73 911s.

The owner came into the shop complaining of a generator light flashing on his early 70's Euro MFI 911 and it was low oil. Yes, I have the PET CDs & download the diagrams but I still have to perform due diligence if it is not an EZ fix. Follow the published info but do not wear blinders on early 70's cars. Just saying what worked for me back in the day. Just trying to add alternative avenues of tracing problems if the M/C is not the fix.

[HarryD]

Originally Posted by Dodge Man

I have A VERY EARLY 73(9/72) and there are many earlier parts like cloth 356 rear brake line straps. Porsche never throws anything away. So wiring not to published spec may not surprising because there were lots of part year changes in the 72-73 911s.

The owner came into the shop complaining of a generator light flashing on his early 70's Euro MFI 911 and it was low oil. Yes, I have the PET CDs & download the diagrams but I still have to perform due diligence if it is not an EZ fix. Follow the published info but do not wear blinders on early 70's cars. Just saying what worked for me back in the day. Just trying to add alternative avenues of tracing problems if the M/C is not the fix.

Thanks for the clarification. As you correctly pointed out, trust but verify.

I know what I found in my 1973.5 and suspect the OP's is similar.

[dicklague]

On Sunday I did a bit of checking and found the brake fluid level low.....I do know that in this 1973 911 there is no way that would make the light flash.....but I did top it up.

Today I found some time to check the emergency brake switch......I removed the 3 bolts and raised the brake mount a bit. I really need to remove the seat to get in there, so I just un-plugged the brake light switch. That did nothing.

Next I will check the master cylinder switch.....

by the way I took the bulb out in the meantime!!!

[HarryD]

Originally Posted by dicklague

On Sunday I did a bit of checking and found the brake fluid level low.....I do know that in this 1973 911 there is no way that would make the light flash.....but I did top it up.

Today I found some time to check the emergency brake switch......I removed the 3 bolts and raised the brake mount a bit. I really need to remove the seat to get in there, so I just un-plugged the brake light switch. That did nothing.

Next I will check the master cylinder switch.....

by the way I took the bulb out in the meantime!!!

Dick:

You are duplicating my path to finding a bad switch on the master cylinder. I think you will find a bad switch.

[dicklague]

Originally Posted by HarryD

Dick:

You are duplicating my path to finding a bad switch on the master cylinder. I think you will find a bad switch.

Thanks Harry......seems like that is the last thing to look at.

As I mentioned it would go out with a hard push or 2 on the brakes.....it has stopped doing that now.

Maybe I will have time this weekend.

Will keep you posted.

[HarryD]

Originally Posted by dicklague

Thanks Harry......seems like that is the last thing to look at.

As I mentioned it would go out with a hard push or 2 on the brakes.....it has stopped doing that now.

Maybe I will have time this weekend.

Will keep you posted.

Hi Dick:

Did you ever find the source of the problem?