Hello, the direct answer is: yes - you will need to reconnect the exciter wire.
Some internally regulated alternators are able to 'self excite', but even those which are not often are able to get themselves going providing there is sufficient residual magnetism left in the core
. This is why you are seeing intermittent functioning (as well as reving the engine can at times help 'wake it up'). I had a like situation (caused by a wire failure in the engine wiring loom). Alternator would work, and then stop. Took it in for testing, and it tested fine (as they connected the exciter) and it still worked after I reinstalled it due to the residual magnetism. For a while [IMG]file:///C:\Users\Win7\AppData\Local\Temp\msohtmlclip1\01\c lip_image001.gif[/IMG]
Connect it to some power source that comes on with your engine, a fuel
pump would be fine. You might connect it through a diode and/or light bulb - not sure the specs on your specific alternator, but some need protection on their exciter wire to prevent the alternator from trying to pass high current back through the exciter wire. In any case, adding in a diode or light bulb will not hurt even if it is not needed. (Diode - a standard 2-5A / 25v or higher one will work just fine. Put it so that the 'arrow' points towards your alternators exciter connection)
Related tach: IF it is indeed a tach designed to be driven from the alternator, you would connect it to the TACH terminal. But know that this only works when the alternator is actually charging! So, given the thing with the Excite terminal, if the alternator has not been 'excited' into working, there is no chance for the Tach to work either!
Best of luck, hope this has helped some.