3.0 upgrade tach problem

911novice · 03-25-2003, 09:28 PM

Just completed upgrade from 2.7 to 3.0 and all went well except tach doesn't work. Is this a rewire issue or do I need to replace the tach with an SC version?

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beamonk · 03-26-2003, 04:15 AM

You need to check your 14 pin connector in the rear. The black purple wires need to match. They are in a different position on the 2.7 cars.

911novice · 03-26-2003, 11:19 AM

Thanks, I'll check it out tonight.

75eleven · 03-26-2003, 03:27 PM

I put a 3.0 in my 1975s. The tach wire was seperate from the 14 pin connection.Had to take the black and purple wire out of 14 pin connection from engine harness and splice it to the black and purple wire that was on a 2 wire connector. Then my 1975 tach that worked perfect with the 2.7 did not work. I had bought a spare tach out of a 1974s and it worked pefectly with the 3.0 ???? Electronics are funny things!!

beamonk · 03-27-2003, 03:59 AM

Same with mine. I had to follow the harness down the side of the engind, cut it open, founs the wire, made a jumper wire, works fine.

MotoSook · 03-27-2003, 04:29 AM

When I did my conversion I was told I needed to get an SC tach by a few knowledgeable 911 owners, but I said what the heck lets try it anyways. Well, it worked, a 76S tach. Good luck.

Do I need to revive 27230WDP

911novice · 03-27-2003, 08:04 AM

I was told the same thing, needed an sc tach due to voltage differences. Souk, do you mean that you did the wiring with the original tach or replaced the tach? I need more coffee before my brain starts to work..

MotoSook · 03-27-2003, 08:07 AM

I used my original tach and spliced into the black and purple wire at the wire bundle just as it comes into the engine bay. I can send you a picture tonight if you'd like.

Good luck.

911novice · 03-27-2003, 09:50 AM

A picture would be great. It would save me a ton of time. Thanks!

CamB · CamB's Garage

My '75 had an SC tach in it. I replaced it with a '74 tach.

Direct swap - no spare wires. Therefore the tachs must be compatible.

More useless info:

Then the innards of the SC tach were refurbed and swapped into my '69 tach and the 69 tach now has an input compatible with an aftermarket EMS. Looks like '69 tach, works like SC tach. cool.