Stolen from a Mustang blog.


"You have a black wire with a red stripe that is attached to the post on the back of the alternator marked 'Grd'. This is, that's right, the ground. This is basically one wire with three ends. One end is attached to the alternator, one end is attached to the engine block on the same bolt that the negative battery cable is attached to, and the third end goes through the headlight harness and is attached to the radiator core support with one of the screws that holds the voltage regulator onto the car."

 

So, is the circular wire connected with the two wires going to it supposed to be grounded to the engine block?

 

Barman10 : I can Post an illustration showing the connections to the Alternator, but first need to know a couple of things that do make a difference.

1) The harness that you pictured is for a 289 that has the in-dash Tachometer Option - is that what you have ?

2) Does your car have the Thermactor System ?

Bob

 

I do not have an in dash tach and I do not have the air pump pollution control system. Thanks for your help!

 

Looks like the engine Block Ground to me as was suggested above.

)

Tony K.

 

Here is how it is wired on my 67 289 coupe

 

Welcome to VMF.
That is not where the ground wire is supposed to be connected. If you look at the diagrams in the post below yours you will see the proper location for the ground wire attachment.

 

As note previously, the harness you pictured is not for a 289 without the in dash tachometer. The correct harness only has two wires with rubber boots on them. A harness with three rubber boots is either for a 289 with in dash tachometer, or for a 390.

Attached are illustrations showing first the 289 without tachometer, and secondly, a 289 with tachometer.

Hope this helps.

Bob

 

Right. The alternator harness for a car WITHOUT the in-dash tachometer (aka has an ammeter) will only have 3 connections at the alternator, not 4... BAT, FLD and a ground. The STA post will remain unused.