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Author Topic:   Tach Hook-up Help
HHuggins
Gearhead

Posts: 259
From: Laguna Niguel, CA
Registered: Feb 2001

posted 04-01-2001 04:51 PM     Click Here to See the Profile for HHuggins   Click Here to Email HHuggins     Edit/Delete Message   Reply w/Quote
Okay, assume I'm an idiot (not too hard). Can anyone give me some help in installing an aftermarket tach in my '70 Mach I?

Thanks,

HH

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68fb
Journeyman

Posts: 42
From: LakeStevens, Wa. USA
Registered: Oct 2000

posted 04-01-2001 10:05 PM     Click Here to See the Profile for 68fb     Edit/Delete Message   Reply w/Quote
Do you know if it is a current sensing tach, or pulse sensing tach?
Most after-market tachs I've come across have been pulse sensing, and they only require an input wire to the ignition coil.

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HHuggins
Gearhead

Posts: 259
From: Laguna Niguel, CA
Registered: Feb 2001

posted 04-01-2001 10:10 PM     Click Here to See the Profile for HHuggins   Click Here to Email HHuggins     Edit/Delete Message   Reply w/Quote
Wow - I have no idea. The guy I bought the car from threw it in with the car. I think it is fairly new, so I suppose it would be pulse sensing? Is there any way to tell?

The car originaly had a hood tach, but it was removed when the car was painted a few years ago. The guy gave me that as well, but I don't want to put it on the car.

HH

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68fb
Journeyman

Posts: 42
From: LakeStevens, Wa. USA
Registered: Oct 2000

posted 04-01-2001 11:02 PM     Click Here to See the Profile for 68fb     Edit/Delete Message   Reply w/Quote
Is there a manufacturer name on it? Sun, Stewart Warner?
A pulse sensing tach has a wire that is connected to the coil- terminal and the interruption of the primary ignition circut by the points creates a pulse which triggers the tach. If the tach has two wires, one will usually be a ground.
A current sensing tach is connected in series from the switched 12V from the ignition key and the wire that is connected to the coil+ terminal, and the tach is triggered by electrical current,(factory ford 67 68 mustang/cougar).

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Troy
Gearhead

Posts: 428
From: Wylie, Texas USA
Registered: May 99

posted 04-02-2001 01:52 AM     Click Here to See the Profile for Troy   Click Here to Email Troy     Edit/Delete Message   Reply w/Quote
I have an old Sun tach on my 70 Mach 1. The hookup is pretty simple as long as you know which wire is for what. Mine is a 4 wire hookup as follows:

black = ground. connect to chasis ground.

blue = lights. connect to the fuse block on the headlights fuse.

green = tach trigger. connect to the negative (-) side of the coil.

red = power. connect to the fuse block on a switched fuse (one that only turns on when the ignition key is turned on).

Hope this helps,

------------------
Troy Esrey
1970 Mach 1 351C 4V
Visit Troy's 1970 Mustang Mach 1 Page

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Moneymaker
Administrator

Posts: 27660
From: Lyons, IL, USA
Registered: May 99

posted 04-03-2001 07:24 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
HH, just give us the color codes on the tach wires and I can help you out.

------------------
Alex Denysenko Co-Administrator and Moderator NHRA/IHRA/SRA member
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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HHuggins
Gearhead

Posts: 259
From: Laguna Niguel, CA
Registered: Feb 2001

posted 04-10-2001 12:00 PM     Click Here to See the Profile for HHuggins   Click Here to Email HHuggins     Edit/Delete Message   Reply w/Quote
Okay, it's got every color that Troy pointed out and also a white wire. What would that be?

Thanks,

Harley

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Moneymaker
Administrator

Posts: 27660
From: Lyons, IL, USA
Registered: May 99

posted 04-10-2001 11:55 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
White should be for lights. Are you sure it has 5 wires?

------------------
Alex Denysenko Co-Administrator and Moderator NHRA/IHRA/SRA member
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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HHuggins
Gearhead

Posts: 259
From: Laguna Niguel, CA
Registered: Feb 2001

posted 04-11-2001 02:39 AM     Click Here to See the Profile for HHuggins   Click Here to Email HHuggins     Edit/Delete Message   Reply w/Quote
Yup - five wires:

Thick Blue
Thick White
Thin Green
Thin Red
Thin Black

BTW - It's a VDO tach.

HH

------------------
1970 Mach I
http://www.geocities.com/hh_machi/

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