I am looking for a different tach signal than the blue wire off the 2 prong connector on the dizzy. I installed a new tachometer and am getting crappy readings over 3k.

I want to test the tach signal from somewhere else. The manufacture of the tach said that I should get a signal from the negative side of the coil.

As far as a I know there is none. There is the main power wire, there also is the power wire that runs to the dizzy and that blue wire that runs to the ICM.

Now there are 4 prongs on the coil and only 3 of them have wires running off them. I want to assume that the 4th prong in the coil is the negative signal the tech was talking about. I just want to confirm it first.

Ive also heard that you can get a signal from the cyp or ckp I forget which one, Ive never tried it.

 

There is a tach wire output on the harness connection on the driver side of the car near the shock tower.

 

That is the one that I am using

 

If you have a meter you can always set it to your lowest AC voltage setting and probe the wires coming off of the distributor. Look for one that is fluctuating slightly at idle and then rises when the engine is revved accordingly. I don't know if this will work for your application however I install car breathalyzers and we have to get a tach signal to tell us when the engine is running, when we can't use the tach test blue wire we look for the non common fuel injector wire and t-tap into it. It won't affect the operation of the fuel injector so long as there is no signal being sent to that wire just sent out. Hope this helps.

 

It might help to list what car you have. Also the tach brand as well. Also most tachs require you to cut the small wires for 4 cylinders. Does yours have that? You could also get it at the ECU

http://www.hksusa.com/content/pdf3375.pdf

 

Ok its Obd1 H22 a in Prelude chasis. Glowshift series 7 95mm.

According to your diagram I can splice it off the a21 ICM signal as well?

 

I dont know what type of signal that the tach looks for, but I imagine its negative since the directions say to tap into the negative side of the coil.

If I tap into a non common injector wire, I would only get 1/4 the ammount of pulses set to the tach and would have to change it to a 1 cylinder tachometer to get correct readings.

But idk what pulses the injector wires send out, being positive or negative. I know that the common wires on the injectors are the yel/blk wire and that is a positive signal that is grounded out at the main relay.

 

Good call for this man, works fine now