Have a ford 555d that the alternator started to lock up and broke the belt. Alternator spun but was hard to turn. Replaced the alternator and belt. Started machine up and it isnt charging. Noticed that the warning light did not come on with the key on. Pulled the wire at the alternator for the light circuit and ground it and the light came on so the warning circuit is okay. Checked voltage at the B+ wire and it was battery voltage. When the engine is running I have battery voltage at the warning light, the B+, the black wire beside the B+. The last wire only has .6 volts on it with the engine running or not with the key on. I am wondering if that should have half voltage to excite the alternator or do I have a bad alternator.