[BTELL67]

Hey guys,
MSD 6AL, Blaster 2, and dist. Had OE tach plugged into box and got nothing. After reading posts, switched tach wire to neg coil post. Still nothing. Pulled out gauge cluster and took photo of PCB. Any connections missing? Anything?

 

[BTELL67]

Hooked up tach adapter today. Getting reading now, but seems low and slow. Oh well, it's a 45 yr old tach right??!! LOL.

 

[Farm Boy]

You can adjust the tachometer. There is a potentiometer on the tach for calibrating it. You can access it thorough a hole in the back of the tach housing. The hole on mine was covered with a small piece of paper. I suggest you use a small plastic screwdriver. You can get a plastic screwdriver at Radio Shack. Hook up a known good tach to your engine and dial in your tach to match it.

 

[BTELL67]

Can I rent that gizmo you got to calibrate from an auotparts store?

 

[BTELL67]

Cool Steve! I was wondering what the hole was for. Mine is not covered by the paper anyore.

 

[mahunt]

Doesn't the 6AL box have a tach feed from the box?

 

[BTELL67]

Yes

 

[BTELL67]

False alarm. Tach not working . Vibration is moving the needle. Aarrggghh!

 

[69-Pace]

You should use the Tach feed on the box with the filter in-line

 

[BTELL67]

I'm using the Tach adapter into the box. Does the Tach filter do something different than the Tach adapter?

 

[BTELL67]

UPDATE:
So I'm back to diagnosing the tach prob before I move on to an aftermarket.
I got correct voltage from 6AL box tach out put and tach adapter. MSD told me to check the printed circuit for the line on the pink 12v wire to make sure the 12v is making it from the harness to the tach. However, he said the parking brake uses the same circuit so if it is working then that means the circuit is good and the tach must be bad. The tach is doing nothing. It moves from 500 to 1000 rpm if your rev it enough but it seems to just be moving from vibration. Im gonna fiddle with that calibration screw and see if that does anything.
Any thoughts out there?

 

[69-Pace]

UPDATE:
So I'm back to diagnosing the tach prob before I move on to an aftermarket.
I got correct voltage from 6AL box tach out put and tach adapter. MSD told me to check the printed circuit for the line on the pink 12v wire to make sure the 12v is making it from the harness to the tach. However, he said the parking brake uses the same circuit so if it is working then that means the circuit is good and the tach must be bad. The tach is doing nothing. It moves from 500 to 1000 rpm if your rev it enough but it seems to just be moving from vibration. Im gonna fiddle with that calibration screw and see if that does anything.
Any thoughts out there?

Do you have a engine analyzer? I'd double check that you are getting any signal from the box or coil over the feed line.

Then bench test the Tachometer by shunting power and ground then tach signal feed direct to the tach bypassing the PCB and harness wires.
If that works then the issue is in the PCB, if it doesn't work then the Tach needs work or replacing.
If it works then add the PCB and shunt power and tach feed to the right circuit ribbons on the PCB. If it still works then you have a possible power or ground issue with the unit or the connector to the PCB. If it didn't work just shunt power and grounds but run the same new lead to the tach feed from the coil. If that works then the feed line is bad in the harness. PITA process but it is the only way to isolate where the issue is.

 

[BTELL67]

Uh.hhhh. what?
Shunting?

 

[69-Pace]

Uh.hhhh. what?
Shunting?

To shunt is to bypass existing routes through existing harness or other connections.

 

[154567]

Take tach to gage shop. Have them check it out. Probably dead. OE tachs and OER tachs don't get along well with MSD electronics. There is a thread on here about tach filters. Check it out. I sent my dead OER tach to redline gage and had modern electronics put in it for the cost of a new tach. Can't tell the difference.

 

[BTELL67]

So i did some more testing in the cluster. Got 12v at the PCB line on brown and pink, and 12v at both tach posts. So I am now at the point where I am comfortable stating my tach is dead.
However, I fiddled with the tach adjustment screw on the back it seems to jump slightly when acceleration occurs. I am still convinced that the tach is bad. Already started installing my Sun Super Tach II.
Thanks guys!!

 

[BTELL67]

Hey Cool Rock,
I thought of putting the guts of the Sun tach in the dash using the orig tach face. Decided not to go through the hassel.
How come MSD stopped making the Lazer Tach?