Problems With 911 Tach and MSD

[Mario.D]

I instaled a 911 Tach in my VW Kombi Bus 911 2L S and MSD-5 ,& the tach
have a malfunction when is conected.
The problem disapear when don't use the MSD.
In the past i used a normal VDO tach with a same MSD-5 without problems.
Somebody have a idea wich is the problem?
This engine use a stock distributor with point & condenser and the MSD-5
is to use with point.
Maybe a Porshe 911 tach is not to use with a MSD?

Regards.
Mario

[kdanie]

Many factory tachs don't work with MSD ingnitions. My VDO tach in my BMW won't work off the ignition box but works if I take the pulse off the + terminal on the coil. Try that and see if it works. MSD makes two types of signal adapters to make their tach signal work on factory tachs-they sell for about $30 or so. Call them if you want to use the adapter so you can be sure you get the model that will work with your tach.

ken

[Mario.D]

Thanks Ken,i will tray with a + in the coil.

Regards.
Mario

[NO_H2O]

I think the Neg. terminal is the point you want to take the pulse from. The + terminal will just put 12vdc on the sense line to the tach and could damage it.

[Mario.D]

Yes is a risk,i contacted MSD technical suport and them recomend use
a Tach controler PN8910 to control the -pulse to the tach.

Thanks.