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1980SCMan
Join Date: Jun 2009
Location: San Diego, CA
Posts: 398
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Brake Light Sending Unit
1980 911SC. My brake lights are out. Easy enough to test the bulbs with the emergency flashers. I can look at fuses. Is there a way to test the sending unit on the master cylinder? It would be nice to be sure before ordering a part.
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12-01-2010, 07:51 PM
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AutoBahned
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sure - do you own a multimeter?
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12-01-2010, 08:27 PM
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1980SCMan
Join Date: Jun 2009
Location: San Diego, CA
Posts: 398
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Yes. I do. Is there a way to check across the unit for resistance? Do I need to remove the unit from the master cylinder?
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12-01-2010, 08:51 PM
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Happiest when Tinkering
Join Date: Jun 2007
Location: Missouri
Posts: 4,558
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Those brake light sending units are pretty much crap they cant take the current put through them (search on the forum) do yourself a favor and install a mechanical brake light switch and bypass the stock hydralic switch I did 26 years ago and havent looked back.
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" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go! 76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3 76 Blazer also restored by me |
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12-02-2010, 03:51 AM
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abides.
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Just short the wires that attach to the switch. If that makes the lights turn on, your switches are bad.
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Graham 1984 Carrera Targa |
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12-02-2010, 08:46 AM
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Senior Member
Join Date: Nov 2000
Location: Great NorthWest
Posts: 3,936
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If it is the switch...
Factor in rebleed on brakes unless you are very good (fast) at R&Ring tapered thread items in a fluid system. If it is the original 30-year old MC, you might consider a new unit - the factory switches on the new MC are superior to the VW items, and at the cost of the switch you might just pitch good money after a new MC to remove any doubt about the seals, etc.
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'78 Targa in Minerva Blue |
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12-02-2010, 10:56 AM
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Happiest when Tinkering
Join Date: Jun 2007
Location: Missouri
Posts: 4,558
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Great time to change out your fluid but as I said the hydralic switches fail fairly quick now days.
__________________
" Porsche there is no substitute" I always liked that saying. Air cooled is the only way to go! 76 911 C.R.A.P. Gruppe #2 BIG time TURBO C.R.A.P. Bitz EFI/EDIS Now MegaSquirt 3 76 Blazer also restored by me |
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12-02-2010, 11:12 AM
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1980SCMan
Join Date: Jun 2009
Location: San Diego, CA
Posts: 398
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My repair didn't go the way I planned. Duh.
I replaced the sending unit about 18 months ago, so I was surprised that it failed so soon, but the forum says that they do fail more often than you'd hope for. This is a daily driver and I'm commuting by using hand signals to keep from getting ticketed or rear ended, so I took it to a local independent. Nice guy - charged me $40 to put the new unit in - total - parts and labor. And he did it on the fly. I was in and out in 20 minutes. Brake lights work now. Here's the new problem. Now the brake indicator light is coming on the dash. Stays on. I can shake it off by cycling the E-Brake but it comes back as soon as I touch the brakes. So did I get a bad sending unit or does it seem that there is more going on here? New Master Cyl within 30K miles. No apparent leaking anywhere and reservoir is steady full. |
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12-02-2010, 09:46 PM
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1984 Porsche Carrera Targa
