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Join Date: Jul 2005
Location: Dyke, Virginia
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Question Brake Pressure Flashing Light

Please explain what brake pressure flashing red light means and how do I stop the blinking. Also OXM sensor?

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mikey3fingers
Old 06-28-2006, 09:46 AM
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Hi Mike,

I am having the same problem at the mo!

See this thread:

http://928uk.myfastforum.org/ftopic84.php

I have discovered that you can clear the fault by disconnecting the battery but it appeared again 3 journeys later!

I am going to change the pads and bleed the system then see what happens. After this I will check the fuses/relays/electrics etc but I don't want to rule out that it could actually be brake circuit failure.

My car is an 83 S Euro spec.

Best wishes,

Llew
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928uk.myfastforum.org
Old 07-03-2006, 11:45 PM
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Llew, Thanks for you advice. Please keep me posted on your sucess. Would like to solve this problem myself. Could a very good mechanic on American cars do this work, or do I have to take it to the porsche blood bank. Thanks, Mike, located outside Charlottesville, Virginia
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Old 07-04-2006, 08:14 AM
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The brake master cylinder has two pressure sensors to warn you if there is a loss of fluid or seal leakage on the front or back. If your brakes are good and you aren't losing fluid, one or both of the sensors are bad. The sensors are available as OEM or generics. I have used the generics for about three years with no problems, but others haven't been as lucky. BTW the warning system often doesn't work properly if two different brands of sensors are used, so replacing in pairs is recommended.

Pelican Parts have both types for the early cars. They are listed as brake light switches.
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Last edited by DPW928; 07-08-2006 at 08:16 PM..
Old 07-08-2006, 07:58 PM
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Lucky me as my '79 started with tail lights out with dash indicator, so I changed both pressure switches as advised here. Now I still have lights out with dash indicator, PLUS I now have the Flashing Brake Pressure lights - an additional Bonus! I tried a three wire jumper to bypass the pressure switches with no change at all. Now thinking this car is going to become the worst decision I have made (it was my first marriage) as I really just want to fix this so I can sell it.
Old 10-14-2013, 12:33 PM
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Even the nicest 928 should be considered a project car.
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1982 Porsche 928, Auto, 4.5
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Old 10-14-2013, 12:48 PM
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Quote:
Originally Posted by '79 Dk. Green View Post
Lucky me as my '79 started with tail lights out with dash indicator, so I changed both pressure switches as advised here. Now I still have lights out with dash indicator, PLUS I now have the Flashing Brake Pressure lights - an additional Bonus! I tried a three wire jumper to bypass the pressure switches with no change at all. Now thinking this car is going to become the worst decision I have made (it was my first marriage) as I really just want to fix this so I can sell it.
Mike, forget about anyone who does not know the 928 working on this - contact Jim Doerr ( jim@928classics.com ) he is in Richmond and see who he recommends.

From the owners manual.
BRAKE PRESS warning light flashes if one
of the circuits in the brake system should fail.

Because of the way the two pressure switches work, you can't easily bypass them - a flashing brake light indicates brake circuit pressure failure or low fluid level - There are two circuits, up to '83 front left and rear right, front right and rear left; '84 on circuits are divided by axle, front and rear.. If one fails the other continues to provide reduced braking, and the light flashes continuously.
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81, 86 928 widebody.
1929 Model A Street Rod 270hp, V6
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Last edited by neil30076; 10-15-2013 at 06:25 AM..
Old 10-14-2013, 01:11 PM
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Okay, trying to keep the frustration down I did as advised and disconnected the battery for a bit. Now the brake lights are working again (dash tail light indicator also out) but still getting the flashing pressure light because the new rear switch seems to have a small leak. When I replaced both switches I just tightened them with a wrench. Are they to be fully seated real tight? Can they be turned too far in? Is there a specific amount of turns? I just removed the old ones without counting turns, etc. I didn't apply any sealer to the threads, I figured the blue stuff they came with was sealer. Although frustrated on this, it is not toward any of you, to the contrary, I appreciate all advice-Thanks!
Old 10-15-2013, 03:16 PM
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Quote:
Originally Posted by '79 Dk. Green View Post
Okay, trying to keep the frustration down I did as advised and disconnected the battery for a bit. Now the brake lights are working again (dash tail light indicator also out) but still getting the flashing pressure light because the new rear switch seems to have a small leak. When I replaced both switches I just tightened them with a wrench. Are they to be fully seated real tight? Can they be turned too far in? Is there a specific amount of turns? I just removed the old ones without counting turns, etc. I didn't apply any sealer to the threads, I figured the blue stuff they came with was sealer. Although frustrated on this, it is not toward any of you, to the contrary, I appreciate all advice-Thanks!
Disconnecting the battery will not clear a 'serious' fault. It will come back on immediately, as there is no memory in an 79 to remember it.
Use no sealer, and the thread is tapered so it will seal fully - give it another 1/8 to 1/4 turn.
And tell us at least where you are, US vs. ROW sometimes makes a difference.
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81, 86 928 widebody.
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Last edited by neil30076; 10-15-2013 at 03:41 PM..
Old 10-15-2013, 03:37 PM
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Check out this post, I had the same issue, check for leaks and then buy 2 new switches from Roger or Mark.

Intermittent Brake Pressure warning light - Rennlist Discussion Forums
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Old 10-17-2013, 12:53 PM
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I am located North of Seattle. So from your answers and what I noticed last check, I am going to give these new switches one more go. I know the rear one has a small leak, likely enough to trip it. I will tighten it a bit more, clean the area real well and check for any fluid leak. I will try to see if it is leaking at the fitting above, or the pins of the switch. Now I know "where" it is leaking determines the switch condition. Now that I have brake lights again, at least getting somewhere. Will return with further feedback.

Old 10-20-2013, 01:32 AM
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