Looking for the Tach wire
Thread Starter
Pro
Joined: Aug 2001
Posts: 626
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From: Lake Lure NC
Looking for the Tach wire
I have just installed a 2 inch stewart warner tach and shift light in my pillar gauge pod. My vette is a 1992 LT1 396. I have not added an aftermarket ignition, do to my worries it contributes to opti damage. I am on the original opti and it is working, so I am keeping my fingers crossed. Where is the factory tach wire located and will I be able to spice into it to get my new tach to work? I do have a MSD 6AL however unless I have to use it, I perfer not to.
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The tach wire is a white wire in a grey connector at the coil. There is a tach filter inline on this wire and the filter is taped inside the engine harness. Do a search on "tach filter" to see if connecting a second tach will cause any problems.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
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From: The Motor City
Originally Posted by mothersworry
Does anyone know if running two tachs off of one filter or wire will cause a problem?
Thread Starter
Pro
Joined: Aug 2001
Posts: 626
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From: Lake Lure NC
Thanks for all the information. I am doing the job tomorrow and want to make sure the understand. I am going to tap into the white wire out of the grey connector attached to the coil. I will tap in between the filter and grey connector to get a direct feed (unfilter) tach signal. Am I correct?
Last edited by mothersworry; Jun 16, 2006 at 11:25 PM.
Thread Starter
Pro
Joined: Aug 2001
Posts: 626
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From: Lake Lure NC
Ok guys, I tap into the tach wire and I am now getting a tach reading to my stewart warner tach. Here is my problem. The stewart warnertach is 800 RPM off my factory tach. How can this be?
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Le Mans Master
Joined: Feb 2005
Posts: 5,146
Likes: 3
From: The Motor City
More than likely it will not be accuratte. The scanner and datamaster show what the ecm "sees", but the dash tach would probably need to re-calibrated. The aftermarket probably reads more like scanner numbers.
Thread Starter
Pro
Joined: Aug 2001
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From: Lake Lure NC
I scanned tonight with my Diacom and the factory tach and the Diacom are exactly the same. I am now confused. The tach and Diacom read 968 and the new electronic tach reads 1876. That is a big difference. Any ideas?
Burning Brakes
Joined: Oct 2005
Posts: 798
Likes: 116
From: OAKLEY CA
Some tachs require an adapter to read accurately. Single fire or double fire ingition is the problem. At least that is what I found installing a tach on my motorcycle. See if the RPM is doubled at higher RPMs also.
Ask about installation on the Tach makers web site if possible. Hope this helps.
Ask about installation on the Tach makers web site if possible. Hope this helps.
Burning Brakes
Joined: May 2005
Posts: 920
Likes: 56
From: Muskoka Ontario
Mothersworry, did you get your tach problem solved ??????????? I just got a shift light and a pod for my 93 and would like to hear if yours is working alright now. Also where did you end up getting your signal.
Thanks
Fred
Thanks
Fred
Thread Starter
Pro
Joined: Aug 2001
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From: Lake Lure NC
Mine is working great. I had to set the Pulses Per Revolution on the tach correctly. Once I set the PPR it worked perfectly. I tapped into the white wire off the grey connector coming from the coil. Easy install. The new tach and shift light works perfectly
