Hoping someone can point out what I might be missing with this issue because it's slowly driving me insane...
Carburetted L98 in a street/strip 68 Camaro, running an LS1 Mitsubishi alternator (used on ~2001-2006 Commodores in Australia or Pontiac GTOs for you guys in the States) with the two pin connector:
![Image]()
![Image]()
![Image]()
Purchased a brand new genuine GM alternator when the conversion was first done. Pin A was looped to alternator post, pin B to light in dash (switched 12V). This ran fine for a few initial startups until I received low voltage warnings and determined I fried the alternator. I suspected my wiring was incorrect and I had burnt up the voltage regulator - confirmed this on the test bench.
A bit of research indicated using an arbitrary 470 ohm resistor to drop the voltage seen on the exciter wire with little explanation why 470 ohms specifically and a lot of people seemed to be parroting information, but for the sake of the exercise I decided to try it with another brand new genuine GM alternator. Pin A rewired to the starter post to sense true battery voltage, pin B to light in dash with 470 ohm resistor inline... nothing, zilch, nada. Alternator did not charge and checking voltage at pin B indicates a large voltage drop with the 470 ohm resistor inline, likely to the point the alternator wasn't being excited therefore not charging.
More research indicated the exciter circuit needs to see somewhere between 5-8V to work correctly so a quick calculation using ohms law to determine the correct resistor needed for the desired voltage drop was done, the resistor was soldered inline, voltage at pin B was checked and within the 5-8V range, hence test three began. Success! Or so I thought... Alternator seemed to be charging, voltages where I'd expect over three or four quick test drives, all seemed fine until Saturday just gone... Car had to be moved out of the workshop and subsequently sat for most of the day outside with the battery connected. Went to fire it up in the late afternoon to move back inside and had absolute nothing at the hit, battery was drained. Charged it enough to get it started and moved inside and called it a day.
Next day, charge battery to a healthy capacity and performed a test to determine parasitic draw. Multimeter showed 4.7A with key off.. way too much and little surprise why I had a drained battery. Disconnected cable from BAT+ to alternator post, current draw drops drastically to ~80mA. My instant thought was a diode had gone out within the alternator but after doing a diode test with the multimeter (one probe on alternator post, one on case, and vica versa), the diodes seem to be fine.
So this is where I'm currently at - one fried alternator with a second likely the same and still no answers as to what I'm doing wrong. I've completed many other LS conversions with zero alternator issues so it's throwing me off as to why I have these issues now. Can anyone shed some light on where I'm going wrong here?
Carburetted L98 in a street/strip 68 Camaro, running an LS1 Mitsubishi alternator (used on ~2001-2006 Commodores in Australia or Pontiac GTOs for you guys in the States) with the two pin connector:
Purchased a brand new genuine GM alternator when the conversion was first done. Pin A was looped to alternator post, pin B to light in dash (switched 12V). This ran fine for a few initial startups until I received low voltage warnings and determined I fried the alternator. I suspected my wiring was incorrect and I had burnt up the voltage regulator - confirmed this on the test bench.
A bit of research indicated using an arbitrary 470 ohm resistor to drop the voltage seen on the exciter wire with little explanation why 470 ohms specifically and a lot of people seemed to be parroting information, but for the sake of the exercise I decided to try it with another brand new genuine GM alternator. Pin A rewired to the starter post to sense true battery voltage, pin B to light in dash with 470 ohm resistor inline... nothing, zilch, nada. Alternator did not charge and checking voltage at pin B indicates a large voltage drop with the 470 ohm resistor inline, likely to the point the alternator wasn't being excited therefore not charging.
More research indicated the exciter circuit needs to see somewhere between 5-8V to work correctly so a quick calculation using ohms law to determine the correct resistor needed for the desired voltage drop was done, the resistor was soldered inline, voltage at pin B was checked and within the 5-8V range, hence test three began. Success! Or so I thought... Alternator seemed to be charging, voltages where I'd expect over three or four quick test drives, all seemed fine until Saturday just gone... Car had to be moved out of the workshop and subsequently sat for most of the day outside with the battery connected. Went to fire it up in the late afternoon to move back inside and had absolute nothing at the hit, battery was drained. Charged it enough to get it started and moved inside and called it a day.
Next day, charge battery to a healthy capacity and performed a test to determine parasitic draw. Multimeter showed 4.7A with key off.. way too much and little surprise why I had a drained battery. Disconnected cable from BAT+ to alternator post, current draw drops drastically to ~80mA. My instant thought was a diode had gone out within the alternator but after doing a diode test with the multimeter (one probe on alternator post, one on case, and vica versa), the diodes seem to be fine.
So this is where I'm currently at - one fried alternator with a second likely the same and still no answers as to what I'm doing wrong. I've completed many other LS conversions with zero alternator issues so it's throwing me off as to why I have these issues now. Can anyone shed some light on where I'm going wrong here?
