83 Jetta Alternator problem!!

Hey there I have a 83 Vw jetta 1.8 gas, I seemed to have run into a problem anmd cant figure it out. I got the car from a friend it had sat for 6 months started up first time drove fine for 2 days then, Car started tp die I figured it was a batteruy problem, but i soon realised it was the alternator. The alternator light comes on and wont go off, So i replaced the Battery And bought a New alternator But the, Alternator for some reason wont work, my car runs at around 12 volts instead of 14.2 meaning the alternator isnt on, I check all the connections and they seems to be fine Could this problem have anything to do with a broken wire or a starter by any chance. Thanks to anyone who has some suggestions.

Did your new alternator come with a voltage regulator, or did you have to transfer it from your old alternator? You should probably check it either way. The battery cable may be corroded. Sometimes the cable gets corrode on the inside at the alternator side. Also, check for belt tension and slipping.

Good luck, charging problems can be a major pain. Once you checked those simple things, the only thing to do is to start from the alternator, and work your way out until you find something wrong.

Make sure the battery light is lit with the engine off and key on. Make sure the alternator is grounded. Make sure the red wires on the alternator are hot all the time.