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There's always something..

Well, I got her running, and a couple days later my "Brake pr ( ! )" light comes on. I looked in the owners manual and the closest thing I can find is the "Brake Press" (brake pressure) light so I assume they're the same. So I checked the brake fluid and its fine, brakes work as good as ever, so I disconnected the battery and the light goes away. 20 minutes ago it starts flashing at me again! So anyway, what else should i check?

I have read online that the sensors on the master cylinder are pretty common to go out. How do i determine if they're bad? I think they're like $30 each (and i think there's two), so thats not too bad, but I hate wasting money only to have the light come back on.

My dad mentioned that the Master cylinder could be giving it up, how do i determine this?

Or it could just be a 30 year old car that likes flashing all the lights it can, but I'd prefer to prevent a brake problem rather than have them go out on the highway.

Thanks in advance!

P.S.
Anyone notice that the (major) problems seem to wait for other ones to be resolved before showing their heads, instead of piling up at once? Or is that just me? Advanced German engineering or coincidence?
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"Weissach" 1982 Porsche 928 auto

Last edited by camo; 01-02-2013 at 03:48 PM.. Reason: P.S.ing
Old 01-02-2013, 01:05 PM
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Take a picture of the cluster so that someone here can verify what the warning light is for. I, for one, have no idea what warning indicator you are referencing.
Old 01-02-2013, 03:43 PM
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It was hard to get a clear picture since its flashing, also the (!) Light/button on the center console is flashing too

Is it just me, or does the 928 have a beautiful instrument cluster? Y'know, if you can get past all the blinking red warning lights!
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"Weissach" 1982 Porsche 928 auto

Last edited by camo; 01-03-2013 at 02:47 PM..
Old 01-02-2013, 03:54 PM
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here is a link to the owners manuals you will find the meaning of the warning lights

Owner's Manual - Online - Rennlist Discussion Forums
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Old 01-02-2013, 04:46 PM
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Thanks MrMerlin, but I have already checked the manual and can't find the exact light.closest I can find is brake pressure.
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Old 01-02-2013, 04:56 PM
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928: Serial Enabler
 
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Group A failure.
Brake circuit / pressure.
(this warning is discontinued after 83).
Requires battery disconnect to reset.
Indicates some sort of pressure related brake failure


Regarding sequential failures, yes.
Nested failures also.
Takes a deep dive and much proactive repair and replacement of failure prone parts, aka throwing parts at it, to restore one to reliability.

If you don't own the copy of morehouse CD sold by Roger, then either buy it or sell the car.
The layman descriptions of all these little nuances, model year by model year, are buried in that CD.

Last edited by Landseer; 01-02-2013 at 06:40 PM..
Old 01-02-2013, 06:32 PM
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Ok, thanks Landseer, I'll check that out
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Last edited by camo; 01-02-2013 at 06:44 PM..
Old 01-02-2013, 06:35 PM
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Takes a deep dive and much proactive repair and replacement of failure prone parts, aka throwing parts at it, to restore one to reliability.
Well said Landseer. I'm just starting my parts throwing.
Old 01-02-2013, 07:52 PM
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Landseer, Where can I get that?
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Old 01-02-2013, 07:56 PM
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Roger at 928rus.com I think has the CDs.

Pretty sure I had that same light come on, usually it means the differential pressure switch at the brake master isn't making a good electrical contact. Disconnect and reconnect the wire may fix it.

The "P" in PM is preventive, ie replacing parts on a still working basis using estimates of the known service life.
Old 01-02-2013, 08:04 PM
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Thanks danglerb, I'm slowly learning that. By the time you finish replacing every part in the car, its time to start over.
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Old 01-02-2013, 08:07 PM
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Hey, I feel your pain, US 83 and a rough but frisky Euro S 85, that very much want attention I can't give them at the moment, and are letting me know it.

MOST of what we face though isn't the need for unreasonable PM, its 30 years of neglect.

Within the 928 community we have a LOT of daily drivers, and moderately to extremely reliable cars, but most of them have a long history of good service.

The 928 does NOT like being parked outside. Its the worst thing for any electrical system, condensing humidity, that thing that happens to our cars every morning outside when all the metal parts are cold enough to have moisture condense on them.
Old 01-03-2013, 03:22 AM
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If your brakes are as good as ever, why throw parts/$ at it????? If the car sat that could have something to do with pressure sensors being stuck. If you have good brakes i would keep an eye that there are no fluid leaks in the system and just drive...My older Brother Frank always said "there are Mechanics and there are parts replacers" He said this to me as i blew every paycheck on my '64 VW when i was 20.
It probably just needs to be driven and try a thorough bleeding..
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Old 01-03-2013, 06:44 AM
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I think I'll try disconnecting and reconnecting the brake pressure switches, replace them, and maybe bleed the brakes. If that doesn't fix it I'll just hope my brakes don't go out

Can anyone post a link to the pressure switches? I can't find them anywhere.
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Old 01-03-2013, 12:46 PM
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After connecting a jumper to bypass my alarm system (thanks again Landseer), my warning light was gone. I started getting excited! until i realized i had disconnected my battery -.-


I will be working on figuring out this warning light after I get back in town, in between classes...
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Old 01-03-2013, 02:44 PM
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928: Serial Enabler
 
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Guys, I'm no expert, but I've rescued 5.
Most were non runners.
3 sit outside in the weather in Indiana, 2 still in Virginia.
They are completely reliable as DD cars.
Each to his own strategy, but mine is working.
I've figured out where to spend and where not to spend.
I always rebuild the brake calipers.
So far never the master cyl.
All electrical sensors get replaced.
Lots and lots of electrical cleaning and wire tracing and repair.
Mainly sweat equity.

Last edited by Landseer; 01-03-2013 at 03:16 PM..
Old 01-03-2013, 02:58 PM
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Quote:
Originally Posted by Landseer View Post
I've figured out where to spend and where not to spend.
Thats what i need to learn!
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Old 01-03-2013, 03:07 PM
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Since you solved my last problem, what would you suggest I start with Landseer? Pressure switches?
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Old 01-03-2013, 03:30 PM
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Brake light switch
Old 01-03-2013, 07:30 PM
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Thank you danglerb! That helped.
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Old 01-03-2013, 07:48 PM
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