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Registered
Join Date: May 2001
Location: San Diego
Posts: 940
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Need help with tachometer
I have a 74 tach and I was told that there is a separate piece (transducer?) that is located in the rear to the left of the engine.
I need this piece. The newer tachs (74plus) have this piece inside the tach. I am trying to get the tach to work with a 3.6 Motor. other suggestions? |
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01-19-2004, 12:48 PM
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Join Date: May 2003
Location: Manhattan Beach, CA
Posts: 2,350
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Your old tach requires a high voltage signal from the coil and not from the DME
output. I don't remember ever seeing a tranducer on any early car. Just connect the tach wire (purple/black) to coil side which goes to the ignition unit.
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Have Fun Loren Systems Consulting Automotive Electronics '88 911 3.2 '04 GSXR1000 '01 Ducati 996 '03 BMW BCR - Gone |
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01-19-2004, 07:09 PM
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Join Date: Dec 1999
Location: TX USA
Posts: 9,804
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NO, no, no ... none of the 2.4 or 2.7 tachs required the ballast-resistor assembly mounted on the relay/fuse/regulator panel! It was phased out during 2.2 engine production.
As far as the 2.4/2.7 tachs go, some will work with the DME output, and some won't ... it is a matter of sensitivity. The Voltage 'swing' of a DME signal is not quite as great as the solid-ground signal from points ... and the 100 Ohm pullup resistor to +14 Volts. Give the tach a try hooked directly up to the DME signal ... it won't hurt the tach, and it might work fine!
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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01-19-2004, 07:34 PM
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My 74 tach worked just fine with the 3.6 until I swapped everything for 964/993 gauges. Just give it a try. I am sure it'll work just fine.
 Ingo
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1974 Targa 3.6, 2001 C4 (sold), 2019 GT3RS, 2000 ML430 I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs Porsche "Hammer" or Porsche PST2, PIWIS III - I can help!! How about a NoBadDays DualChip for 964 or '95 993 |
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01-19-2004, 08:26 PM
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Join Date: May 2001
Location: San Diego
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I did try it briefly before I discovered my engine was crap and needed rebuilding, and it did not work.
When I sold the previous engine I gave the new owner everything on the panel next to the engine. So when the tach would not work I started to wonder if I gave away something I needed. I also had some strange issues with the alternator light, When the key was in the off position the light stayed on. So I will be chasing this down too. I did talk to Patrick Motorsports today, in their conversion harness they put a voltage amp to raise the signal out of the DME for the earlier tachs so I need to check this to make sure there is no issues with the soldier connections. Last edited by scca_ita; 01-19-2004 at 08:40 PM.. |
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01-19-2004, 08:38 PM
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Join Date: Dec 1999
Location: TX USA
Posts: 9,804
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An IRF9630 or IRFD9123 HEXFET buffer ought to do the trick ...
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Warren Hall, Jr. 1973 911S Targa ... 'Annie' 1968 340S Barracuda ... 'Rolling Thunder' |
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01-19-2004, 08:54 PM
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Registered
Join Date: Nov 2006
Location: Norway
Posts: 25
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Sorry about my "english" guys !!!
Taco-Tachmeter- or what ever you call it, please try it in my langvitch: "turteller" Thanks for all the advises !!! |
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04-08-2007, 05:23 AM
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1974 Porsche 911 Targa 3.6
