I have an mostly stock c6, bcm still fitted. the stock alt on these cars is kinda junk. aftermarket is super expensive and still kinda blah. it's a 4 pin setup with 12 sense wire, a turn on signal at the L terminal and a pwm load signal back to the ecm.
I picked up a cheap used 2 wire alt from a newer truck. these default to 13.8v. they need a pwm on L terminal to change voltage.
10% = 11.0 V
20% = 11.56 V
30% = 12.12 V
40% = 12.68 V
50% = 13.25 V
60% = 13.81 V
70% = 14.37 V
80% = 14.94 V
90% = 15.5 V
in hp there's a drop down box under voltage control from the stock "not fitted" alt to "fitted". I do seem to be able to get some pwm put out.
but the bad part, I only get the output of I go under scanner special settings and manually turn the L terminal on. soon as I do that the voltage jumps from the default to 14.9ish which seems about 85% duty cycle. if i unselect it, it goes back to default. if I hit off button it doesn't charge at all. which is also weird since you leave it completely unplugged and it still charges at default.
so I have 2 problems, one I don't know why it doesn't turn on the L terminal request on its own after cranking. 2. how do I adjust the duty cycle? I changed some settings and flashed but nothing changed at the meter when manually turned on.
there's a few threads come up under search, but most are for stand alone without a bcm. I still have mine.
any thoughts?