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How can I test a speedo sensor on 915 box?
Hello,
My speedo doesn't work (didn't since I got the car last year - must likely because of a re-wiring botchjob before). The speedo itself is new and I am tracing the wires to check them. Anyone know how I can check the actual electronic speedo sensor that mounts on the side of the 915 gearbox? i.e. Ohms across it, etc. Thanks for your help! BRD Last edited by brd; 08-01-2010 at 02:24 AM.. |
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08-01-2010, 01:33 AM
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Just put the meter set to Ohms across the 2 leads in the tunnel, as you rotate the wheel you will see it pulse.
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Ed 1973.5 T |
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08-01-2010, 04:13 AM
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Ahhh... perfect. Thanks!!
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08-01-2010, 04:39 AM
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Join Date: Dec 2009
Posts: 825
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need sensor i have a good used one
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08-01-2010, 09:28 AM
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Just checked the sensor... all fine there. Am checking the wiring on the speedo now.
You happen to know which wires go where? I have two speedos... a 260kph one (I think) and a 300kph one. They have different pins being used on the back. The 300 one has +, 2 (not used), A, 31b, - The 260 one has +, 2 , A (not used), 31b, - I'm guessing the two signal cables go to 2 or A and 31b.... and other two are power and ground? I am actually not sure which one is the right one... 260 one was in car (it's new), but never worked - which I'd blame on bodgy wiring that I have been fixing these last months. Thanks for your help!!! brd. Last edited by brd; 08-01-2010 at 10:44 AM.. |
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08-01-2010, 10:40 AM
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Just a hint, but info on the car and engine helps when asking questions.
Here is a pic I found doing a search. 12V power goes to the top+ terminal, ground and one lead of the speed sensor goes to the bottom - terminal, and the other leg of the speed sensor goes to the 31b terminal. 
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Ed 1973.5 T |
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08-01-2010, 11:32 AM
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Your completely right Ed.... Its an 81 SC engine with 915 box in a 1970 911T... and the existing wiring is a repair job... which I tried to do right with the correct colours etc... but prefered to work with the connector references on the back of the speedo. I found that post too with that pic... followed it... found the SC wiring diagram (also here on fabulous Pelican) and saw the little detail that sorted everything: One of the speedo sensor cables has to go to that ground pin on the back of the clock with a spade splitter connector. The second goes to 31b... then add 12v to + pin... and rock n roll!!!
I'll check thats its reading right enough next time out with a TomTom. Thanks for everyones help... again!  BRD |
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08-01-2010, 12:09 PM
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Porsche 911T
The Other Woman
