You should examine the exisitng wires in case the insulation is worn through somewhere and is shorting to ground. Assuming the alternator is OK, there are only three connections to check. 1. The first is the ground connection, which is a no-brainer as the alternator bolts to the engine block, and the starter works, so this connection must be OK. 2. The second is the connection between the battery and the alternator output. It is common practice to have this a fuse wire. If the old alternator's output shorted, then the fuse wire would blow - if you look carefully there may be signs of heating of the insulation. In any case check it out with a meter or trouble light. (A trouble light between ground and the alternator output terminal should always show full brightness (battery voltage). If the fuse wire is toast, I just get two 30amp pigtail fuse holders and wire them in parallel (for 60 amps) and then run a fresh wire to the battery. Make sure this wire is a heavy enough gauge to handle 60 amps. (I've seen Bosch alternators that use insulators on the output terminal and the fuse consists of a tiny fuse link between two insulated washers. This link can corrode away, and people will usually replace the alternator, when all they needed to do was replace a cleverly hidden fuse.) 3. The third connection is the power to the internal voltage regulator of the alternator. This is fed from the oil pressure switch that closes when oil pressure builds up(unlike a idiot light oil pressure switch that closes when oil pressure falls). You want to make sure this terminal sees battery voltage (it may be somewhat less than full battery voltage as in many models this is fed through an idiot light or a 10 ohm resistor) when the engine is running. PlEASE NOTE: There are alternators available that are "self exciting", which do not need this last connection (3.). Perhaps the one you replaced was one of these, and the wiring to provide the exciting voltage is not fully functional for the model of alternator you now have. N.B. Be sure you wiggle the wires when checking the connections, as loose and intermittant connections can drive you batty. If the battery connection and the exiting voltage connection are OK, it's time to check the alternator again, as an alternator output wire momentarily shorting to ground can blow out the alternator and wiring harness.
