Speedometer Wiring

Here is the current wiring situation. Anyone who can help, I would really appreciate it. I can't stand it when I make things worse in my attempts to repair something. Is it possible to burn up the speedo or sending unit by miswiring the gauge? Here are the details:

The car is an 82 SC.

Here's what I have, not counting the bulb wires, which I know are hooked up correctly (I did leave one bulb out to match it up, could that cause the problem?):

9 wires bundled with double connectors into 3 sets of 2 wires and 1 set of 3 wires. The set of 3 wires are all brown and I assume they are grounds.

A set of two wires: 1 black and red, 1 black and blue. These are currently hooked to the + terminal as the wiring diagram indicates.

Another set of two wires: both brown and red.

A set of two wires: 1 white and red, 1 black and brown.

The wiring diagram I have from the Pelican site shows a brown/red, green, and brown wire going to the "-" terminal.

It shows only 1 brown/red going to the "31b" terminal.

It shows only 1 white/red going to the "A" terminal.

I have no green wire, and I swear that all three brown wires were the only ones connected to the "-" terminal. The parking light indicator works correctly the way the wires are connected.

The only connection that matches the wiring diagram exactly is the 1 black/red and 1 black/blue hooked to the "+" terminal.

I am almost totally sure that all the wires were in pairs using double spade connectors at the terminals except for the brown set, which had two wires going to one spade for a total of 3 brown wires.

I'm hoping that you can help me sort this out if you're familiar with the wiring. I hope I didn't fry something by having it connected wrong.

Thanks in advance,

Olivier
82 SC

Olivier,

OK, if there is one thing good about the situation, it is that you have the +12 V leads hooked to the correct terminal! Other than the ground (-) connections, the only connections that are important for the speedometer function are the two Brown/Red wires ... they are from the two sensor leads on the transaxle. I believe that sensor is a 'Hall Effect' magnetic switch, and since the leads are the same color code, it should not matter which one goes to ground or which one goes to the 31b terminal.

Was/is your car a Euro market car, or a USA model, because that could make a difference in the wiring diagram?

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Warren Hall
1973 911S Targa

I did finally get the speedometer to work. I must have hooked it back up wrong once and fried the circuit board. Two connections on the ground circuit were burnt up when I finally took the speedometer apart. After some ugly but functional soldering and more studying of the wiring diagrams, the speedo works again. I think I need to calibrate it, though, since I turned the adjustment screw when it was apart. Does anyone know how to set the adjustment? I have a multimeter and it doesn't look like something you can do while you're on the move, even with someone else driving.

I appreciate the help. The cruise control wire was what was making the wiring diagram confusing. For future reference, the 3 browns plus one brown/red (the one with the double spade connector) go to the "-" terminal. The other single-plug brown/red wire goes to terminal "31b". The red/black and red/blue go to the "+" terminal, and the white/red and the brown/black for the cruise control go to the "A" terminal.

Thanks again,

Olivier