MSD install no tach

[Amstaff]

Originally Posted by timmy2

Well, if you have continuity from the tach adapter purple wire all the way to the tach, and the car runs normally, then I think it is time to test the tach or the MSD unit and adapter.
Do you have access to a working tach you can borrow or the instruments and ability to test the tach?
If not, send it out.

No access to another tach.

Where is the recommended place to send it for a checkup?

[timmy2]

I have read that North Hollywood in CA is very good.
(Have them install a voltmeter in the gauge while you are at it...)

Try the test of pulse grounding as mentioned by Johnny?

[fred cook]

When I put an MSD 6A in my SC, this is how I wired it:

CDI Plug......................................MSD Wires
1 System Ground ......................................Black coil wire
2 Tachometer Signal..................................Black wire from left end of MSD unit (Tach )
3 Signal Grd (Green wire shield) Grd............Purple wire
4 Coil Hot +12 volts...................................Orange coil wire
5 Switched +12 volts..................................Small red wire
6 Signal (Green wire center conductor) Pos...Green wire

Heavy red wire +12 volts (wire to starter terminal
Heavy black wire Grd. (wire to chassis and engine)


I did not use the White MSD wire. Hope this helps

[Amstaff]

There are two diagrams one is:

"Wiring a Current Triggered Tach to Points/Amplifier or Magnetic Pickup" where the purple (violet) wire is not used and the red wire from the tach adapter is the trigger wire (to the tach)

The second says "Wiring with a Magnetic Pickup Distributor and a Voltage Triggered Tach". on this one the red wire from the adapter goes to keyed power and the purple goes to the tach.

I have it wired like the second one. Red to keyed power and purple to tach.

From the tach adapter both show black to ground and white to tach output on the MSD box

Is this correct or should I be using the first setup?

[Amstaff]

Anyone?

[Jonny H]

Tom, why don't you try momentarily grounding the TD wire as per my previous post. Simple and free! Let me know what it does,

[Amstaff]

Originally Posted by Jonny H

Tom, why don't you try momentarily grounding the TD wire as per my previous post. Simple and free! Let me know what it does,

What wire is the TD wire?

[timmy2]

Wire the adapter the other way and see what happens?
"What is the worse that could happen" is our district Engineer's favorite saying!

[Jonny H]

TD, tacho drive. Apart from 12V and ground, it is the only other wire on the back of the tacho. It is clearly marked 'TD' on my SC but not sure about the 2.4

[Jonny H]

Ok, it is marked different on your car but it's the purple and black wire.

[Amstaff]

I assume that is the purple wire. I disconnected it at the engine and grounded it.

Nothing happened. The tach didn't move at all.

[Jonny H]

Provided you had the igntion on I think your tacho is broken.

Reading back through the thread, you had a 50/50 chance of frying it by connecting it to the coil. if you connected it to the '+' terminal then I'm afraid you put around 350V into it which isn't very friendly.

[Amstaff]

The ignition was on.

Guess I will pull it and send it out for repair.