Joined: Feb 2019

Posts: 8

Likes: 0

Hey all,

i found out the hard way my new alternator has a parasitic draw by finding a dead battery this morning. The diodes in the alternator test fine when checked with the diode settings on my multi meter but the test light shows a draw when run from the negative cable to the output stud with the battery disconnected. I have another alternator that wasn’t charging but has no draw when tested so I swapped the rectifier to the new alternator and it still has a large parasitic draw. I thought only a bad diode would cause this. When I test the old alternator with the new alternators rectifier it does not have a draw. So swapped everything between the alternators beside the windings and cases and it’s still acting the same way. I’m stumped what else in the new alternator would cause a draw strong enough to kill a new battery in two days of sitting. My truck is an 84 with a 94 alternator swapped in and no external regulater anymore.