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Registered
Join Date: Oct 2004
Location: CA
Posts: 5,857
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Short in the brake circuit: popping fuses like crazy!
I have a 69 (it's a 912, but ignore that for a second) that started popping the brake light fuse each time I press the brake pedal... How would I got about diagnosing what is causing the short ? ( I already ruled out turn signals which are on the same circuit)
I pulled the bulbs and it still pops the fuse when I press the pedal, so bulbs are out, that leaves the brake switch, the wiring and the brake light housing, right ? I removed those to inpect the wires, but I can't see anything obviously frayed except for one ground wire that is frayed where it touches the body, one inch from its connector, but that means it should ground even better, I guess... Any idea on the most efficient way to troubleshoot this? I don't want to start snipping wires for nothing... I should mention the PO wired in a 3rd brake light too, so I'll look there as well... Looking for a smart methodology or trick here... Thanks ! |
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04-11-2009, 08:34 AM
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Join Date: Oct 2006
Posts: 452
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Removing just the bulbs was not enough. It may be in the socket. Before you get into that, disconnect the 3rd brake light and see if that helps. Ideally, you want to disconnect the hot lead at the socket to isolate that particular unit. May end up being the switch itself. I'm leaning toward the 3rd light or one of the other sockets though.
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pozee |
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04-11-2009, 01:35 PM
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Happiest when Tinkering
Join Date: Jun 2007
Location: Missouri
Posts: 4,581
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does the brake switch at the pedal see 12 v or see ground?
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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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04-11-2009, 04:42 PM
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Registered
Join Date: Oct 2004
Location: CA
Posts: 5,857
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I got it guys, thanks, good advice ! I did the sockets, the 3rd light, but it still popped ! Turned out I found a 3rd wire at the brake switch where there should only be 2 (69 is mechanical, which is much smarter than the hydraulic one on my SC) that presumably went to power the 3rd brake light. Disconnecting it at the switch (vs at the other end, at the 3rd light) fixed my problem. I guess that wire is frayed and grounded somewhere along the way, and it's not worth tearing the carpet apart to fix ! Took me about 10 fuses to get it... $2.50 ;-)
Moral of the story: if you are popping fuses, check your wires for grounding ! |
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04-11-2009, 06:55 PM
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