Aftermarket Tach... wiring?

[Scotty]

Pita: Series IV, negative ground, 1725 w/ Hitachi Alt and Weber 32/36

A friend gave me one of those off-the-shelf Tachs you'd get from an Autozone. It was a nice gesture and I really didn't want to refuse it. I was wondering if it could be wired in? Do you need to loop it? Do they even work? Thoughts?

 

[sunalp]

Without seeing what it is and how it wires it's kinda hard to tell. It may be very simple. Does it fit in the dash?

 

[Tom H]

I would guess that an "off the shelf" tach from Autozone would be easily wired into a SIV with Neg Earth. I would expect that it has 3 wires or connections, Gnd, +12 V power , and a wire that would go to the side of the coil that is wired to the distributor, which would provide 12 V pulses once per spark. I would expect that the tach has some way of setting the number of cylinders in the car it is being installed in.

As I said these are guesses and expectations, but you really need to read the instructions for the tach to know for sure.

 

[husky drvr]

I would guess that an "off the shelf" tach from Autozone would be easily wired into a SIV with Neg Earth. I would expect that it has 3 wires or connections, Gnd, +12 V power , and a wire that would go to the side of the coil that is wired to the distributor, which would provide 12 V pulses once per spark. I would expect that the tach has some way of setting the number of cylinders in the car it is being installed in.

As I said these are guesses and expectations, but you really need to read the instructions for the tach to know for sure.

Tom,

There might be a wire for instrument lighting - maybe.

Just a thought,

Don

 

[Scotty]

I would guess that an "off the shelf" tach from Autozone would be easily wired into a SIV with Neg Earth. I would expect that it has 3 wires or connections, Gnd, +12 V power , and a wire that would go to the side of the coil that is wired to the distributor, which would provide 12 V pulses once per spark. I would expect that the tach has some way of setting the number of cylinders in the car it is being installed in.

As I said these are guesses and expectations, but you really need to read the instructions for the tach to know for sure.

Plus Husky's post and yes, four wires and the Tach is set up as you said. I had an issue with how I had my Coil wired and fixed that so it's all negative ground (Don't ask). Even with everything right, the Tach isn't picking up signal no matter which side of the coil I plug it into or anything. 12V+ is being plugged into one of the prongs on the back of the ignition switch. I've had it ran directly on 12V just to make sure it was getting power and it's just a brick.

What am I missing?

 

[Bill Blue]

What do you mean when you say you've had it directly on 12v? Something has to be wrong, either bad connection or bad tach. Since the light works, I'd question the tach 12v source.
Bill

 

[Tom H]

OK, so you have 4 wires. Are they labeled , color coded, or what,? What does the instructions say about which wire goes where? How do you set the tach for 4 cyl or 6 or 8 ? Bill said you said the light works, but I don't see where you said that. Does the tach light work?

Tom

 

[Scotty]

OK, so you have 4 wires. Are they labeled , color coded, or what,? What does the instructions say about which wire goes where? How do you set the tach for 4 cyl or 6 or 8 ? Bill said you said the light works, but I don't see where you said that. Does the tach light work?

Tom

Four wires, red, green, black, white. Red goes to 12V+, Green is Signal, Black is Ground, White is for the light. There's a slide switch on the back for the Tach to be set at 4, 6 and 8 cyl.

The Tach light works. I used the source of the light to test 12V+, so I know I'm getting juice. Ground is being screwed into the body where the Control Box was grounded. That one I sanded to bare metal and am using a new screw. Signal is plugged into Coil - on a spade next to my Distributor plug, also plugged in Coil -.

I'm going to assume that the Aftermarket Tach is what's bad?

 

[Tom H]

Yup, sounds like a bad tach. Is there a brand, and model number on it? One simple fix to try is to move the slide switch to 8 and then back to 4. maybe a couple times. Slide switches sometimes get their contacts corroded a bit.

 

[Scotty]

Yup, sounds like a bad tach. Is there a brand, and model number on it? One simple fix to try is to move the slide switch to 8 and then back to 4. maybe a couple times. Slide switches sometimes get their contacts corroded a bit.

The Tach was bad. Went and installed a different one and it worked. Very bright and easy to read, especially at night. Considering swapping out instrument lights for LEDs now and putting money together see about getting the Jaeger Tach rebuilt. Back on the road, thank you guys!