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Is it possible to run two Tachs at the same time? #106081 08/16/08 08:32 PM 08/16/08 08:32 PM
Joined: Jun 2008 Posts: 114 USA S stan1970 OP member
stan1970 OP member S Joined: Jun 2008 Posts: 114 USA	I suspect the Sun tach (looks to be somewhat old) in my 1970 Coronet is not reading accurately at higher RPMs. "Feels" like it's ok at idle or low RPMs. I've heard that some older tach have problems with Mopar electronic ignition, so I'm not sure if this is a factor. I was wondering if it would be possible to have two tachs running a car simultaneously?? From what I remember, a tach gets it's info from the negative side of the coil, right? If I had another tach and powered it from the right source and added it's wire to the one from the Sun tach at the coil now, would that work? Thanks a lot! --Stan

Re: Is it possible to run two Tachs at the same time? [Re: stan1970] #106082 08/16/08 08:37 PM 08/16/08 08:37 PM
Joined: Jan 2003 Posts: 32,943 Grand Prairie,Texas stumpy I Win
stumpy I Win Joined: Jan 2003 Posts: 32,943 Grand Prairie,Texas	I don't see why it wouldn't work.

Re: Is it possible to run two Tachs at the same time? [Re: stumpy] #106083 08/16/08 08:44 PM 08/16/08 08:44 PM
Joined: Jan 2003 Posts: 75,042 U.S.S.A. JohnRR I Win
JohnRR I Win Joined: Jan 2003 Posts: 75,042 U.S.S.A.	yes i have , tic toc tach and a stewart warner , but with points .

Re: Is it possible to run two Tachs at the same time? [Re: JohnRR] #106084 08/16/08 08:51 PM 08/16/08 08:51 PM
Joined: Nov 2007 Posts: 1,522 Orleans, Ontario moparcanuk pro stock
moparcanuk pro stock Joined: Nov 2007 Posts: 1,522 Orleans, Ontario	I've run a factory tach and Dixco tach at the same with points and also with electronic ignition.

Re: Is it possible to run two Tachs at the same time? [Re: JohnRR] #106085 08/16/08 08:51 PM 08/16/08 08:51 PM
Joined: Jan 2003 Posts: 5,791 Hamilton, Ontario Canada Magnum master
Magnum master Joined: Jan 2003 Posts: 5,791 Hamilton, Ontario Canada	I've seen factory and aftermarket tach running together many times. 2 aftermarket ones can't see why not but I've never seen it. Do you have a timing light with a tach? 69 Super Bee, 93 Mustang LX, 04 Allure Super

Re: Is it possible to run two Tachs at the same time? [Re: Magnum] #106086 08/16/08 10:21 PM 08/16/08 10:21 PM
Joined: Jun 2008 Posts: 114 USA S stan1970 OP member
stan1970 OP member S Joined: Jun 2008 Posts: 114 USA	Thanks all for your answers! Regarding Timing light -- I just have a basic one -- no tach on it. I suspect my old Sun tach is not accurate at higher RPMs, so wanted to hook up another to verify before yanking it out and discarding it. When I take off in the car (4speed w/ 4.10 gears in the rear), it feels like it's revving very high and I have to shift, but generally the tach is showing less than 2000 RPMs. So, I figured that can't be right.. So, it sounds like I can have two wires going to the negative side of the coil for the two tachs. I was just thinking that somehow they might interfere with each other, but it sounds like a lot of folks run this way already. Thanks !

Re: Is it possible to run two Tachs at the same time? [Re: stan1970] #106087 08/16/08 10:46 PM 08/16/08 10:46 PM
Joined: Feb 2003 Posts: 4,798 Castlegar, BC, Canada That AMC Guy master
That AMC Guy master Joined: Feb 2003 Posts: 4,798 Castlegar, BC, Canada	Tone Generators are great for this kind of thing. Every pulse sensing tach can be re-set correctly using a pulse generator. Believe it or not, anybody with an audio editing program and a line out jack can create their own tone generator Very helpful when recalibrating old tachs. Bloody Mary, Full of Vodka, Blessed art thou among cocktails....

Re: Is it possible to run two Tachs at the same time? [Re: That AMC Guy] #106088 08/16/08 10:55 PM 08/16/08 10:55 PM
Joined: Apr 2008 Posts: 1,195 Snowing in the north! D Dart 340 moparts member
Dart 340 moparts member D Joined: Apr 2008 Posts: 1,195 Snowing in the north!	Yes, it will work fine.

Re: Is it possible to run two Tachs at the same time? [Re: That AMC Guy] #106089 08/16/08 11:01 PM 08/16/08 11:01 PM
A Anonymous Unregistered
Anonymous Unregistered A	Quote: Tone Generators are great for this kind of thing. Every pulse sensing tach can be re-set correctly using a pulse generator. Believe it or not, anybody with an audio editing program and a line out jack can create their own tone generator Very helpful when recalibrating old tachs. (Ahem...) My age is showing. In the mid '60's I build an Allied Radio "Knight kit" tach, and they had you calibrate it using a high value resistor off the AC line as a pulse source. Nowadays, that would be a gigantic liability. I would suspect that if you hooked ENOUGH tachs up all the same time, you'll eventally load down the ignition, but I doubt two of 'em will do it

Re: Is it possible to run two Tachs at the same time? #106090 08/16/08 11:05 PM 08/16/08 11:05 PM
Joined: Jan 2003 Posts: 70,126 Here DirectSubjection Tacohead. The First and Only
DirectSubjection Tacohead. The First and Only Joined: Jan 2003 Posts: 70,126 Here	I have one in my dash for driving and one under the hood of my Duster for tuning, both wired to my MSD's tach terminal. Ride eternal, shiny and chrome

Re: Is it possible to run two Tachs at the same time? [Re: stan1970] #106091 08/17/08 01:14 PM 08/17/08 01:14 PM
Joined: Jan 2003 Posts: 2,874 Upstate, NY sixpack4spd master
sixpack4spd master Joined: Jan 2003 Posts: 2,874 Upstate, NY	Quote: When I take off in the car (4speed w/ 4.10 gears in the rear), it feels like it's revving very high and I have to shift, but generally the tach is showing less than 2000 RPMs. What does the tach say when you are going 70MPH in 4th gear???

Re: Is it possible to run two Tachs at the same time? [Re: sixpack4spd] #106092 08/17/08 02:48 PM 08/17/08 02:48 PM
Joined: Feb 2003 Posts: 21,318 Manitoba, Canada DaytonaTurbo Too Many Posts
DaytonaTurbo Too Many Posts Joined: Feb 2003 Posts: 21,318 Manitoba, Canada	Just add the extra one in and splice it in to the feed lines of the old tach. Will work fine.

Re: Is it possible to run two Tachs at the same time? [Re: sixpack4spd] #106093 08/18/08 12:25 PM 08/18/08 12:25 PM
Joined: Jun 2008 Posts: 114 USA S stan1970 OP member
stan1970 OP member S Joined: Jun 2008 Posts: 114 USA	Thanks all for the help! sixpack4spd - it shows under 3k RPMs in 4th gear at around that speed... which I don't think can be right...

Re: Is it possible to run two Tachs at the same time? [Re: stan1970] #106094 08/18/08 12:43 PM 08/18/08 12:43 PM
Joined: Jan 2003 Posts: 32,943 Grand Prairie,Texas stumpy I Win
stumpy I Win Joined: Jan 2003 Posts: 32,943 Grand Prairie,Texas	Punch your #s in here and see what you get. http://vexer.com/68rt/speed.html Figure your tire diameter here. http://www.procomptires.com/conversionchart.htm Last edited by stumpy; 08/18/08 12:47 PM.

Re: Is it possible to run two Tachs at the same time? [Re: DaytonaTurbo] #106095 08/18/08 12:58 PM 08/18/08 12:58 PM
Joined: Feb 2003 Posts: 1,142 Tucson, AZ C cruzin super stock
cruzin super stock C Joined: Feb 2003 Posts: 1,142 Tucson, AZ	I just ran into the same question a few months back when I went to install a shift light which has a tach too. I called the manufacturer and was told I could wire it in w/o any affect. Seems to work fine.

Re: Is it possible to run two Tachs at the same time? [Re: stan1970] #106096 08/18/08 01:37 PM 08/18/08 01:37 PM
Joined: Jan 2003 Posts: 4,727 Moved to N.E. Tennessee GomangoCuda master
GomangoCuda master Joined: Jan 2003 Posts: 4,727 Moved to N.E. Tennessee	Quote: I suspect the Sun tach (looks to be somewhat old) in my 1970 Coronet is not reading accurately at higher RPMs. I was wondering if it would be possible to have two tachs running a car simultaneously?? Sun Tachs from the 60's all used a tach adapter box. I don't know what happens if you try to use them without the box. probably doesn't work at all. Chances are your tach isn't that old and it is just bad. As already stated by several others there is No problem hooking up two tachs. In theory, there is no difference between theory and practice. In practice, there is.

Re: Is it possible to run two Tachs at the same time? [Re: cruzin] #106097 08/18/08 07:55 PM 08/18/08 07:55 PM
Joined: Jan 2003 Posts: 70,126 Here DirectSubjection Tacohead. The First and Only
DirectSubjection Tacohead. The First and Only Joined: Jan 2003 Posts: 70,126 Here	Quote: I just ran into the same question a few months back when I went to install a shift light which has a tach too. I actually have two tachs and two shift lights wired up. Ride eternal, shiny and chrome

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