Yes it won't exite propley without that.
Without knowing what type of alternator you have i can only guess at what's present but I had a similar problem putting my spare alternator on.
Sometimes the phase-tap is a bolt, that's common on Fords for example. this is what runs the rev counter as it's connected to only one phase out of 3. Fords use it for carb heaters and stuff.
The battery light (exitation wire) connects to the votage regulator or diode pack. Once you now what to look for it's obvious but they are almost always a regular sized spade or small bolt. It could be it's missing so look for any unusedholes in the rear cover.
Any chance of a picture?