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Eng-o-neer
 
Tremelune's Avatar
 
Join Date: Dec 2011
Location: Los Angeles
Posts: 3,107
Speed sensor, bouncy gauge, sketchy wiring...

The speedometer on my '84 is bouncy, and there's no cable, so I think it's electrical. It is intermittent, and I could have sworn it had something to do with the gear I was in, but that behavior seemed to go away. Indeed, I think the ground is poor, but I don't know how a speed sensor works, nor do I understand how the speedometer gauge works, sooo...If someone could verify my sanity...

I recently had some interior work done, and there are now wires all over the place. I can see the pair of brown/red speed sensor wires, but I'm confused about the brown wires. Two sleeves of wires emerge from the grommet. One is taped off. The other has the two browns...



I'm pretty sure that my speedometer is bouncy because one of the grounds got ripped.



According to this diagram, the snipped wire is likely the one that is the ground for the speed sensor...but all of the speed sensor wires seem to be grounds...Can anyone enlighten me as to how that thing works? There are a lot of wires connected to this ground, so I assume they're grounds as well...The two wires coming out from the grommet are brown, and one of the wires that continues on after the connector is brown/black. I'm not sure I'm even looking at the right wires on the diagram.



Also, does anyone know what this wire might be? I don't remember it being there...My car has a 3.6 swap, so anything goes...


Old 06-08-2017, 12:17 PM
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Eng-o-neer
 
Tremelune's Avatar
 
Join Date: Dec 2011
Location: Los Angeles
Posts: 3,107
Here's another diagram that has a green wire thrown in, which is present in my car, but none of the other colors match:

https://rennlist.com/forums/911-forum/687929-speedo-wiring-84-carrera.html

My diagram above is (supposedly) for an '84...
Old 06-08-2017, 12:21 PM
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Eng-o-neer
 
Tremelune's Avatar
 
Join Date: Dec 2011
Location: Los Angeles
Posts: 3,107
Well, mystery solved to a degree. I put a new connector on for those ground wires and also noticed that the speed sensor wires were loose. I pushed them in tight, labelled everything, and zip-tied 'em to a support under there...



In the interest of beating a thread to death, if anyone knows what any of these wires might be for, just shout it out...At least some appear to be ghosts of an amplifier...











Also, if anyone knows how to stop my coupler from rattling...or keep that rubber boot in place...ah but I digress...

Old 06-08-2017, 02:11 PM
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