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Posted by: DaveO90s4 Feb 3 2017, 11:48 PM

Hi all,

1975 model, now with the infamous flashing brake warning light. I had the oem master cylinder and front callipers overhauled when I bought the car about a year ago. Recently I could hear the flasher unit clicking as I drove, and now this has 'grown' to the red light flashing too. I have confirmed that the park brake switch is working properly. I can stop the flashing only by disconnecting the wire from the reconditioned master cylinder. There is no reset switch on that master cylinder. I am very confident that the brakes are working properly: good pedal feel, stops straight and well, no residual pressure holding any brakes on, etc etc. I have no reason to believe I need to bleed air out of the system or do any other work on the brakes - other than for this flashing light issue.

I've done lots of searches, but other than for disconnecting the offending wire / switch ( which I'd much prefer not to do) I'm unsure what to do next. Maybe buy a new switch for the reconditioned master cylinder?

All suggestions very welcome.

Thanks

Dave

Posted by: Krieger Feb 3 2017, 11:59 PM

Hi Dave. Are you sure there is no switch on the master cylinder? It is on the unit that screws into the side of the master cylinder. The wire your talking about is plugged into it. The "switch" is just a small black rubber pin/nub that sticks out of the side of that unit. Just push it in with your finger 3-4 mm. You can get at it without jacking up the car. Just turn the steering wheel all the way right and get your body on the ground.

Posted by: DaveO90s4 Feb 4 2017, 01:39 AM

Hi Andy, well I'm pretty sure. I looked and looked and looked while I had the car up on the hoist. I'll go and have another look tomorrow and post a photo / findings.

Thanks

Dave

Posted by: bdstone914 Feb 4 2017, 09:12 AM

If there is no switch there must be something in the hole plugging it.

Posted by: Dave_Darling Feb 4 2017, 01:47 PM

See if you can get a decent pic of the switch.

--DD

Posted by: 914Sixer Feb 4 2017, 03:37 PM

Switches from 74-76 all have reset button. Make sure the rubber tip is on it. If it is missing a a small white dowel will be sticking out instead.

Posted by: DaveO90s4 Feb 4 2017, 09:35 PM

Hi all,

Photos attached. Can anyone see a reset switch anywhere?


Attached thumbnail(s)

Posted by: DaveO90s4 Feb 4 2017, 09:36 PM

And one more photo


Attached thumbnail(s)

Posted by: 914Sixer Feb 4 2017, 09:40 PM

Interesting, the switch is a early style with one pole not two. Never seen one like that. I can post a picture tomorrow of a NOS switch with reset button.

Posted by: DaveO90s4 Feb 4 2017, 10:15 PM

Thanks Mark, I'd appreciate that

I see this switch is sometimes referred at as the brake light switch. Maybe the two pole version does activate the brake lights. But not on my car - on my car the brake lights are activated by a contact switch inside the car under the wooden floor boards. That is working properly.

Maybe I need a new single pole switch with reset button?

Dave

Posted by: eyesright Feb 4 2017, 10:59 PM

I tried and tried to fine the cause of my '76 flashing brake light...I hate to admit it but I finally just pulled the lead off the flashing bulb.

Posted by: boxsterfan Feb 5 2017, 12:22 AM

Had same flashing brake light on my 1974. Was never able to find the problem. I too never saw a reset button on the MC. Who's got a pic of one?

Posted by: ndfrigi Feb 5 2017, 03:20 AM

QUOTE(eyesright @ Feb 4 2017, 08:59 PM)

Posted by: 80cap Feb 5 2017, 10:03 AM

This thread just solved a problem I was having! I couldn't find the source causing my flasher relay from clicking. It is the brake switch on the master cylinder. Now I have the same problem as in this thread. I pulled the wire and now more clicking but as mentioned my master cylinder doesn't have a switch.
Brian

Posted by: 80cap Feb 5 2017, 11:42 AM

After disconnecting the brake warning wire from the master cylinder my interior light wont work on the door switches. The ground path to the switches opened. So now I have a continuous buzzer warning when the key is on telling me the brake warning light is supposed to be on but now the interior light works again.

Posted by: Dave_Darling Feb 5 2017, 11:42 AM

The switch without a reset button is supposed to reset itself when the balance between the two circuits is restored. Could be that this one is sticking somehow?

--DD

Posted by: 80cap Feb 5 2017, 11:50 AM

When I get a good pedal I'll let you know. I am also have trouble bleeding these brakes. the system is all new from PMB.

Posted by: 914-300Hemi Feb 24 2017, 06:22 PM

I just replaced my master cylinder from pmb iand now the brake light is flashing. I guess I will reset the wire from the MC and see if that fixes the issue.