Brake lights gone, fuse blows
10-29-2001, 07:46 PM
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Brake lights gone, fuse blows
OK, i'll be the first to admit that I know little about cars. I do know that I love my little 928. Its my first car and I want it to be happy. So, after two weeks of people driving a little to close I found out my car was not very happy. NO more brake lights. First thoughts were to check the bulbs and fuses. Bulbs fine. Hurrah! It was the fuse. I replaced the fuse and my car was happy again. Next morning, people riding a little to close to me again. Look back at a stop light and see no red reflection. Swear for the next 20 mins on my drive to work and verify that indeed my lights are out again. So, I check the fuse and yes, it is blown again. So, I let an electrician friend (k, he works on Plasma Chambers and Ion Sources, but he knows his electrical stuff) check out my car. After an hour he tells me I have a short but he can't find it (while we are at work anyway) and that I should ask around to see if there was a common or likely place that the short might occur. This guy is nice enough to offer to have me come over to his house on a saturday to help me fix it. I'd like to make it as quick as possible for him, anyone have any ideas where we could track this short down? Its getting cold out and my arm is getting chilly hanging out the window doing the little hand signal stop. 
Thanks for any help you can give me ahead of time
Thanks for any help you can give me ahead of time
10-29-2001, 08:47 PM
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Standard introduction:
"Hi, my name is Tom - and I own a 928."
Forum response:
"Hi Tom!"
Owning a 928 for a first car is either gonna spoil you for all others, or make you appreciate low maintenance vehicles in years to come - hah ha!
Anyways, welcome brother Tom to our version of a 12-Step program.
It is always a good idea to include in the body of your post (don't hide it in the title) as much relevant information in a request for assistance - at a minimum, always state the model year, if it is a 5-speed or auto and if it is a Euro or US version.
OK, so back to your query - the bulb sockets tend to get corroded over time - my first suspicion would be to do continuity checks on those to verify that the short is not at the socket. After that I'd look at the brake light switch, located on the brake pedal assembly (someone here can give more specifics if required). Do those checks then tell us what you find, especially if you fixed the problem.
"Hi, my name is Tom - and I own a 928."
Forum response:
"Hi Tom!"
Owning a 928 for a first car is either gonna spoil you for all others, or make you appreciate low maintenance vehicles in years to come - hah ha!
Anyways, welcome brother Tom to our version of a 12-Step program.
It is always a good idea to include in the body of your post (don't hide it in the title) as much relevant information in a request for assistance - at a minimum, always state the model year, if it is a 5-speed or auto and if it is a Euro or US version.
OK, so back to your query - the bulb sockets tend to get corroded over time - my first suspicion would be to do continuity checks on those to verify that the short is not at the socket. After that I'd look at the brake light switch, located on the brake pedal assembly (someone here can give more specifics if required). Do those checks then tell us what you find, especially if you fixed the problem.
10-29-2001, 11:30 PM
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Doh!
Its been a few years and apparently I've forgotten my board etiquette. I appologize. But dont expect me to fall back into practice all at once! =-)
Ok, stats on my baby.
1980, 928 V.8, automatic
You went way past me on the US/Euro thing =-)
Its brown, would that help? Heh.
OK,a few more things i forgot to put in my last post:
You can put a new fuse in and the fuse will not blow until you actually press on the brakes. The lights do come on until hte fuse blows.
My friend had said he thought it was somewhere between the master cyclindar and the lights. I of course know nothing about this but I will pass on what you said to him as well. If the information I gave you gives you any other ideas please let me know and I will pass those on as well.
Thanks again for all your help!
~ Tom
Its been a few years and apparently I've forgotten my board etiquette. I appologize. But dont expect me to fall back into practice all at once! =-)
Ok, stats on my baby.
1980, 928 V.8, automatic
You went way past me on the US/Euro thing =-)
Its brown, would that help? Heh.
OK,a few more things i forgot to put in my last post:
You can put a new fuse in and the fuse will not blow until you actually press on the brakes. The lights do come on until hte fuse blows.
My friend had said he thought it was somewhere between the master cyclindar and the lights. I of course know nothing about this but I will pass on what you said to him as well. If the information I gave you gives you any other ideas please let me know and I will pass those on as well.
Thanks again for all your help!
~ Tom
10-30-2001, 09:31 AM
#4
Tom,
Goes without saying... Welcome.
Now let's see using a simple analogy...
I dropped a bowling ball on my foot and for some reason my foot hurts!
Then the lights work ... UNTIL... I step on the brakes,,,Hmmm?
Randy has you on the right trail! Somewhere between the brake pedal and the bake lights.
Even if the switch is the culprit check those sockets front as well as rear. Go easy on the car wash pressure hose if you use them. AND when you are done checking sockets and screw things back together be gentle a lot of PO's just reefed down -gutten tight-
cracking or distorting the pretty plastic pieces.
Also another good site is
Greg Nichols Homepage http://nichols.nu/tips.htm
Later.
Keep em' rolliing
John S. 82' Weissach, Auto. , 'Pattycakes'
Goes without saying... Welcome.
Now let's see using a simple analogy...
I dropped a bowling ball on my foot and for some reason my foot hurts!
Then the lights work ... UNTIL... I step on the brakes,,,Hmmm?
Randy has you on the right trail! Somewhere between the brake pedal and the bake lights.
Even if the switch is the culprit check those sockets front as well as rear. Go easy on the car wash pressure hose if you use them. AND when you are done checking sockets and screw things back together be gentle a lot of PO's just reefed down -gutten tight-
cracking or distorting the pretty plastic pieces.
Also another good site is
Greg Nichols Homepage http://nichols.nu/tips.htm
Later.
Keep em' rolliing
John S. 82' Weissach, Auto. , 'Pattycakes'
10-30-2001, 09:25 PM
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Welcome to the 'clan' Tom.
Based on your posts - only the actuation of the brake light circuit causes the fuse to blow - Randy has it nailed I think - probably a faulty switch.
btw - noticed in your last post that you Shark has the coveted V8 - wow!!! You one lucky dude there my man. (tongue in cheek)
Based on your posts - only the actuation of the brake light circuit causes the fuse to blow - Randy has it nailed I think - probably a faulty switch.
btw - noticed in your last post that you Shark has the coveted V8 - wow!!! You one lucky dude there my man. (tongue in cheek)
10-30-2001, 10:14 PM
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One technique for finding short circuits that blow fuses:
1) Procure three feet of lamp cord (18 ga two-conductor stranded wire used to go from the wall to a lamp), and a small 12 volt light bulb.
2) Solder the light bulb on one end of the lamp cord.
3) On the other end of the lamp cord, solder one conductor to each end of a blown fuse.
4) Install the blown fuse/light bulb test rig into the brake light fuse position.
5) Remove all brake light bulbs.
6) With the ignition on, press the brake pedal. If there is a short to ground anywhere in the circuit, the test bulb will light. No ground, no bulb lighting. The bulb will limit the power going to ground thru the short circuit, so there is no danger of burning wiring. You now have a very visible tester that will tell you when you have a short circuit.
7) Use a stick to hold the brake pedal down, and start hunting the short circuit. Put the test bulb high enough that you can see it while you are at the back of the car.
1) Procure three feet of lamp cord (18 ga two-conductor stranded wire used to go from the wall to a lamp), and a small 12 volt light bulb.
2) Solder the light bulb on one end of the lamp cord.
3) On the other end of the lamp cord, solder one conductor to each end of a blown fuse.
4) Install the blown fuse/light bulb test rig into the brake light fuse position.
5) Remove all brake light bulbs.
6) With the ignition on, press the brake pedal. If there is a short to ground anywhere in the circuit, the test bulb will light. No ground, no bulb lighting. The bulb will limit the power going to ground thru the short circuit, so there is no danger of burning wiring. You now have a very visible tester that will tell you when you have a short circuit.
7) Use a stick to hold the brake pedal down, and start hunting the short circuit. Put the test bulb high enough that you can see it while you are at the back of the car.
10-31-2001, 11:06 AM
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You should make friends with a 928 mechanic/Porsche shop. There is whole world between the brake pedal and the brake light.
Keep this in mind: Most problems occur somewhere between the front and rear bumper!
Keep this in mind: Most problems occur somewhere between the front and rear bumper!
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12-03-2001, 10:46 PM
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I just wanted to write and thank everyone for all their help and advice. Unfortunately i didn't get a chance to use any of it. Just when I was going to take the car to a friends to work on it, it died. The fuel pump went out on it and i couldn't do a thing. So while it was being worked on, they looked into the brake light problem and fixed that as well. Now on to the little things! Thanks again, and look for me elsewhere on the board!
~ Tom Gallant
Thanks again, and look for me elsewhere on the board!~ Tom Gallant
12-04-2001, 10:26 AM
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Tom:
How about letting us know what the problem was with the brake light? It might be helpful for someone else here now or in the future.
Dave
How about letting us know what the problem was with the brake light? It might be helpful for someone else here now or in the future.
Dave
12-04-2001, 11:16 AM
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Oh, the problem with the brake lights. . . Ok, from what the guy said (and you'll have to just go on what he said, cause i have NO clue, really.) was that the master cyclinder was leaking onto the switches and shorting them out. So to fix it, he replaced the master cyclinder and the switches, i believe. My father came in and took control over the car so I dont really know the whole story. Sorry! =-)
~ Tom Gallant
~ Tom Gallant
