1977 Merc 120 Alternator and volt gauge question

[The Hack Shack]

My alternator is not charging. I have battery voltage on the sense wire, trigger wire and battery wire. I do not know how the volt gauge affects or has anything to due with the alt but it is not currently hooked up. I cannot seem to find a wiring diagram on it, The gauge has a positive, negative and ground terminals. The alt has 4 wires. Help please.

 

[Bt Doctur]

Re: 1977 Merc 120 Alternator and volt gauge question

Orange to battery, should have power
sense lead, should have power
trigger, should have power ONLY with key in run position
black is system ground
Gauge: +12v from ign souorce
ground/ neg. for for gauge and lighting circuuit.