buzzing noise from alternator with key off

[818ortega]

hello, my name is sal and i need some help. i just bought a 77 blazer with a 454 engine out of a 89 chevy truck. the problem is that my battery drains unless i disconnect the battery and there is a buzzing sound that only goes away with the batt. disconected. the alternator is a 3 wire with the conector from the 89 engine spliced to the wires of the 77. i found when i disconect one of the wires from the connector the buzzing goes away. now my question is how do i make the buzzing sound go away and is what might be draining my battery. thank you any help would be appriciated and sorry for such a long post

[j cAT]

Originally Posted by 818ortega

hello, my name is sal and i need some help. i just bought a 77 blazer with a 454 engine out of a 89 chevy truck. the problem is that my battery drains unless i disconnect the battery and there is a buzzing sound that only goes away with the batt. disconected. the alternator is a 3 wire with the conector from the 89 engine spliced to the wires of the 77. i found when i disconect one of the wires from the connector the buzzing goes away. now my question is how do i make the buzzing sound go away and is what might be draining my battery. thank you any help would be appriciated and sorry for such a long post

the alternator is most likely defective...the voltage regulator has leakage to ground...removal of the large red wire and the issue resolved will indicate that the alt. is n/g....the question is what is the correct alternator to use...amps???????

[ortega818]

the cable i disconnect is not the big red wire it's the red wire on the small connector. since this is the alternator has been replaced twice is there any chance it could be the ignition switch that is messing up and still energizing the alternator with the key off.

[MagicRat]

Originally Posted by ortega818

the cable i disconnect is not the big red wire it's the red wire on the small connector. since this is the alternator has been replaced twice is there any chance it could be the ignition switch that is messing up and still energizing the alternator with the key off.

That small connector (with the 2 wires) might be wired up backwards.
One of the 2 wires gets (+) power all the time, the other one gets power only when the ignition switch is on.
Use a testlight on both wires to make sure this is true with the wires on your truck. If so, then try reversing the 2 wires to see if the problem goes away.