Testing tach signal wire?

[bashr52]

My 1980 model year Chrysler (79 date code) has the 1980 Magnapower ignition system, with the white tach signal wire. This runs t my airguide tach, which has 2 wires. One is grounded, the other attaches to this white wire. It is not working however. Is there a way to test the signal from the ignition to determine if that is the problem or if the tach is bad?

 

[jaybirddog11]

Re: Testing tach signal wire?

I believe if all wiring is correct, then running your engine is your test. I am not sure of this, hopefully one of the pros can chime in. Make sure all your wiring is OK. Check for continuity all the way back to your CD module. Also, check the back of the tach for a dial and make sure it is on the proper setting. I recently had to replace my original CD module with one that has no tach wire. I had to buy a new 3 wire tach but was able to get it to work correctly. What is the model number of your engine? How many poles does your stator have?

 

[bashr52]

Re: Testing tach signal wire?

The tach does have a dial, and I clicked it to what is supposed to be the 3 cylinder setting. Hard to tell since the sticker is so old. The regulator has 3 poles, but the tach signal wire comes from the back of the CDI. Mabie the tach is setup to run on the regulator signal instead?

Model number indicated it is a 79, but the boat/engine combo was sold as a 1980. Like I said before, the ignition system matches the one shown in the 1980 wiring diagram.
http://www.maxrules.com/graphics/force/wiring/75-85Motorola.jpg

 

[jaybirddog11]

Re: Testing tach signal wire?

Since your tach signal comes from the CDI, you do not hook it up your current tach to the regulator. Your stator determines what tach you have and what tach you may need to replace it with. You count the poles on your stator, usually 20 poles or 12 poles. The stator is located under the flywheel. You may be able to look under without removing and count the poles. I am not exactly sure how the CDI sends out the pulse to your tach but if your stator is bad, you may not be getting any signals to send to your tach from your CDI. Hopefully one of the pros chime in.

 

[huskerdaninva]

Re: Testing tach signal wire?

If the stator in the attached diagram is correctly represented it is a 12 pole set up.

 

[bashr52]

Re: Testing tach signal wire?

What does the stator have anything to do with my setup if the tach signal is supposed to come from the CD box, not the regulator?

 

[jaybirddog11]

Re: Testing tach signal wire?

Hopefully one of the pros chime in to give you a detailed answer. My understanding is the stator sends power to the CDI enabling the CDI to send the signal to the tach.

 

[bashr52]

Re: Testing tach signal wire?

The stator and CDI are two totally separate systems on my engine.........