trying to install tach

[iceman1]

I have been trying to wire a tach in my truck with no success.
Here’s my set up. I have a pro comp 7000 distributor with 2 wires. One goes to the plus side of the coil for power and the other wire goes to the neg. side for operation. I am trying to install an old tach I bought at a flea market. I believe the tach works as I can pulse the wires against a battery and make the needle deflect. The tach has 3 wires 1 for a light bulb and 2 other wires a marked plus and minus on the back of the tach case.
Here’s what I did. I wired the tach with the light wire going to the dash lights, the plus going to gauge power, and the neg. wire going to the neg side of the coil. It appears that the case is ground for this tach. When the tach is wired to the car it will not start. If the car is running and I plug in the coil wire it will kill the engine, so it appears that it is shorting out the coil.
I was wondering if I need a tach module for this type of distributor or if anyone has any ideas of what else I might be missing?

 

[Old Iron]

Really need more info
Is it an old Sun tach ? If so it requires a sending unit to work and has to be the right one too.
If it's an old Sun tach, pull the tach out of the case and on the back it tells which unit is right.
Sun Tach II it does not require a sending unit.

 

[iceman1]

the tach was a no name one. I did not see a name inside but I will look again more closely. I'll try to figure out how to post a picture. I have heard about the Sun tach and them having modules though and something about an odd battery inside. Were there other manufactures that used modules?

 

[Old Iron]

Right off the top of my head I can't think of any
Most tachs have a red, green, black and sometimes white wire
Red 12v +
Black ground
Green neg side of coil
White lights

This is an old Stewart Warner tach w/sender. Not sure of the hook up to coil though and it's not a very good pic [S

 

[iceman1]

that print is the way i set it up got. the only exception is my tach has only 3 wires with the 4th being the tach itself being ground.

 

[christcrusader13]

that print is the way i set it up got. the only exception is my tach has only 3 wires with the 4th being the tach itself being ground.

any luck with that tac?

 

[iceman1]

sorry I did not get back sooner. No fix figured out. I did look at the tach again and found that it is a Track Tach and was made by Wico. there are no other markings on the tach. I was wondering if there was anybody on the site that rebuilds tach's. At least to check it out to verify it is in working condition as I think it is.

 

[iceman1]

I did a little research yesterday on the internet and found something interesting I want to try this weekend. It seems that there were some tachs that were made to be tied in series in the coil to distributor wire. it says they were not very accurate as the rpms would vary with dwel changes. the way it says to check for this type is to see if the tach is low impediance 1-5 ohms.
this method was used on some of the ford and MOPAR hood tachs.