Tach not working
 

'72 911T with '67 911 engine. I have a Perma-Tune and a Bosch Blue coil, but the tach has never worked, 11 years owned, I'm just starting to do my own maintainence and I want to get this tach working! Where can I begin looking? Thank you for the time.

Is there NO input into your tach or is it bouncing around and giving eroneous readings?

The first thing I'd do would make sure the purple/black wire is plugged in by your distributor.

Is the tach wire in the engine compartment hooked up? Should be a purple/black wire.

I will look for the purple/black wire connected to the distributor. There currently is NO input into the tach, it is not bouncing or giving erroneous readings

The purple/black wire is connected to the dist. cap, then the wire runs, with a bundle of other wires, to the left side of the engine compartment and it plugs into a connector, then I wonder what

I think it may actually start it's run from the negative side of the coil....

83 911 tach
 

hey Tim my name is GAry I have 83 sc my tach does just that jumps around with bogus reading and sometimes operates fine any ideas??

Thanks

tach
 

The SC tach is a magnetic triggered style, you may have to back date the tach or use an MSD box instead of the permatune.
Mike Bruns

There is a different electrical connection to the tach for the different model years.
It is indeed a black/purple wire. On CDI cars up to 2.7 with 3 connections at the CDI unit, it is connected under the relay plate in the engine compartment. Hard to locate.
On cars with 6-connection CDI units, it is connected via the 14-pin connector at the back of the relay plate, thus needs to be reconnected.
Maybe after changing to the Permtune, the connection has been "forgotten"...
jens