86/5.0 32V/Manual/928S

The other night I was driving on the highway. When I taped my brakes, I noticed my amp meter drop and spring back to the 14v position. I did not put these two together for about 15 miles. Sometimes when the volts droped the radio and lights would flash as well. Once I placed all of this to pressing the brake pedal, I got the felling that this could be the cause of all of my electric problems.

Other problems that I am having include the ABS is inop, Cruse control inop, and high beams will not stay on high beams when selected. (this I still think is in the switch)

My question is, could this be a short that could cause the other systems to burn out? Should I be looking for a short in the wire or posibly a relay. And last is there a way to test the relay without replacing it. I have seen them get up there in price, and would hate to buy replacements if they are not bad.
<img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

I was having the same type of problem. I am not sure what it is yet. Things turn off when I step on the brakes. Someone said to check all of the grounds. There may be a poor ground somewhere.

 

Ell-

A bad ground may make sense for the fluctuations in amperage on your meter, but I don't think it would cause the ABS to not work. That being said, cleaning your ground points is not a bad idea as regular maintenance. Your car has 14! Have fun! <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

By the way, I looked at the wiring diagrams for your model year. I couldn't find the ground points for the brake lights, it may require greater studying to track it down, but, that's the ground point I'd start with. I'd also see if you could swap the relays (not sure if you can or not). I'm sure someone out there can tell you if that's doable or not.

Good luck. <img src="graemlins/wave.gif" border="0" alt="[byebye]" />

 

Are you getting a mastercaution warn and/or dash warnings?
Have you cleaned the sockets in the rear light assembly's?
If all of your lights are working but going thru a dim cycle with the voltage drop you might be losing the brake switch itself.
Check the wire 'BOOT' on each switch - both are under the master cylinder - it is a rubber covered connector cover with three wires running to the bottom of each switch.
I'm not sure ... but there should be a relationship between the master cylinder/ pressure sensor switches and the ABS even though the ABS has it's own 'brain' and sensors

 

OK, so far I cleaned the grounds at the Battery to chasy. I cleaned both the ground above the fuse box and on the steering bracket. NO change.

I disconnected the positive wire from the brake switch under the dash and the problem went away along with my brake lights. So I am thinking that the switch is bad.

Is this a common switch that can almost be replaced with any piston switch? I would hate to have to wait and order this part to see if I am right.

Ell <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Ell and Mary,
My Weissach (82') has two and I believe Dennis Wilson said his 79's had two.
Unless there was a change along the line you should have two as well. They live under the Master cylinder -see description- they look like short fat spark plugs once you push the boot off the bottom and remove them. It has a 22 or 23mm
hex on the body -a little more than 15/16" -, overall lenght is about 1 7/8" in heigth from the tips of the three blade type electrical connectors to the tip of the 8 threads that screw into the master cylinder. Dennis recommended replacing both at the same time as they report in to the master caution and the dash warn system which picks up on disparities in resistance similar to the light system - change one...change both and preferably from the same manufacturer.
I didn't have a crows foot for the rachet, maybe you can use one of those old fashioned (cuved bracket wrenches, or heat and bend a wrench to get in there. A regular socket simply won't fit in there as the inner body panel is shaped to go under this area rather closely.
What I did was: Removed air cleaner cover, pulled the driver side air tube out of the way with a bungee, disconnected the 4 way plastic vacuum connector -remember where everything goes, and that one side of the 4 way is actually a plug -
loosened the two flat tip screws between the last 2 driver side intake tubes and removed/tied back the tube. Basically I removed anything that would give me a little more room -I have huge hands-.Don't forget to push off the rubber boot electrical connector at the bottom of each switch and then tuck them out of the way.
After trying all of my mystery tools I gave up and trotted down to WalMart. I bought 2 of the smallest - 7 1/2" long adjustable/crecent wrenches with emphasis on a NARROW body. The switches thread into the bottom of the Master cylinder -electro-hydraulic?- remove the one farthest from the driver first then the one to closest to the driver. It will be slow going at first but after say 2-3 threads the switch came out by hand. Since there will be a little brake fluid loss tape some plastic -trash bag- topped with an old hand towel or T shirt to absorb the loss and protect the paint.
When you reassemble: roll the rubber boot back to make installation easier. Take your time and make sure you don't cross thread.
Hey, from your test description it sounds like your booster is Ok but your master cylinder is failing. If someone else can confirm that; there was a recent post where the guy replaced his Mastercylinder and he said the switches came with it. If you do change the switches and feel the need to bleed -I didn't- there is a small, 6 or 8mm hex on the side of the master cylinder that I think is the bleeder.
Good luck <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Thank you John,

I went out and felt under my master cylnder and there are no switches or wires attached.

The switch that I found matches your discription, however there was only one and it was mounted and activated by the brake pedal itself. I can order and get the switch from NAPA auto for $14.00

Thanks again for the detail of your reply.

Ell

 

John,

In MY84 the brake switch was changed to an underdash VW/Audi part number. <img src="graemlins/cussing.gif" border="0" alt="[grrrrrrr]" />

BTW Bevo is all skin and bones now. <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />

Dennis

 

Do you know what year/make VW or Audi the switch came from? I would think that it would pe cheaper to order it for one of those car's instead of a Porsche.

 

Morning Dennis,
Now I gotta find that other guy and check out his MY...
Say, Dennis. If you should get run over by a bus or get launched off one of those ski jump -speed bumps- they put on Oklahoma's Interstate Highway system... could you put me on the distribution list of your will for for dibs on the manuals
Ell and Mary, sorry ...good thing the oversight committee has eyes like a hawk and a mind as fast as Dan Ackroyd.
So, is this a SINGLE SWITCH? And you can reach it from inside the car? Cripes! I know I said I wouldn't modify Pattycakes but I feel a couple of Mods comin' on.
Dennis in other news...
Steve Ambrose passed on this morning...
How I the hell will I tell my Dad?
A lot of the remaining WWII vets thought of Steve as a re-incarnated Ernie Pyle, my Dad included.
Be prepared for a major shift in Geriatric demographics. I'm predicting a huge attendance at his funeral to include Hollywood and Gov't.
<img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> one for those not here <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

The switch is a single piston action switch with 2 wires. I didn't feel any switches under the master cyl.