Mechman not charging at idle

[asilayinruins]

Sorry, posted this in other thread but didn't get any answers...

 

So I just got my 370 amp mechman rebuilt.  It's for my 08 chevy tahoe.  I used to have the old style 2 pin, but have upgraded to the 4pin style with the one wire for 12v source.

Initially installed it and had the 12v source hooked up to the cigarette lighter fuse under hood.  I noticed at idle, my rpms would dip to 500rpms, and my battery would be sitting around 13.2-13.5.  Once I accelerate, or rpms go over 600, then my voltage would jump back up to 14.5-14.7.

I changed my belt to correct size.

I talked to Tony from Mechman and have since ran the 12v source to another fuse, ECU fuse. I also forgot to ground my alternator to battery, so I did that also.

Seems to be working good after one drive. I notice my idle rpms is now not dipping to 500, and it stays around 600-700 at idle.

 

So question is, was my alternator not running at idle so it wasn't charging batteries?  Can the alternator not being running at idle cause the rpms to dip low around 500? Not sure what was going on.

[Kyblack76]

Because your "turn on " is to low.  (rpm)

[ChevyBoy95]

On 10/7/2023 at 8:30 AM, Kyblack76 said:

Because your "turn on " is to low.  (rpm)

x2 on this. 

 

They need enough rpm's to start outputing. You can change the pulley size to help speed this up without changing the engine rpm. (if the alternator pulley is smaller it will spin faster at the same engine rpm).

 

I ran in to this a bit with my chevy as in drive it would idle around 600 rpm.

[asilayinruins]

On 10/10/2023 at 3:06 PM, ChevyBoy95 said:

x2 on this. 

 

They need enough rpm's to start outputing. You can change the pulley size to help speed this up without changing the engine rpm. (if the alternator pulley is smaller it will spin faster at the same engine rpm).

 

I ran in to this a bit with my chevy as in drive it would idle around 600 rpm.

So I've been noticing that when my rpms go down to 500 the alternator seems to not be turning on. I have the smallest pulley that mechman has on its 370amp alts.  This wouldn't happen to be from one of the fuses im tapping off from, not putting out 12v to turn on the alt when the rpms are at 500? No matter if my rpms are at 500, aren't the fuses, such as ECU or cigarette lighter, suppose to still put out voltage? 

Is the alt still getting a turn on signal at low rpm, it's just that the alt isn't outputting any charge at a low idle? 

[asilayinruins]

On 10/7/2023 at 3:30 AM, Kyblack76 said:

Because your "turn on " is to low.  (rpm)

So I've been noticing that when my rpms go down to 500 the alternator seems to not be turning on. I have the smallest pulley that mechman has on its 370amp alts.  This wouldn't happen to be from one of the fuses im tapping off from, not putting out 12v to turn on the alt when the rpms are at 500? No matter if my rpms are at 500, aren't the fuses, such as ECU or cigarette lighter, suppose to still put out voltage? 

Is the alt still getting a turn on signal at low rpm, it's just that the alt isn't outputting any charge at a low idle? 

[Kyblack76]

On 10/24/2023 at 9:10 PM, asilayinruins said:

So I've been noticing that when my rpms go down to 500 the alternator seems to not be turning on. I have the smallest pulley that mechman has on its 370amp alts.  This wouldn't happen to be from one of the fuses im tapping off from, not putting out 12v to turn on the alt when the rpms are at 500? No matter if my rpms are at 500, aren't the fuses, such as ECU or cigarette lighter, suppose to still put out voltage? 

Is the alt still getting a turn on signal at low rpm, it's just that the alt isn't outputting any charge at a low idle? 

All alts have a "turn on" rpm.  Im a bit lost on you "tapping" a wire from anything. Even then, that shouldnt matter. The alt, has a turn on rpm.  The simple connector should have you not tapping into anything, but, i dont know your rig, build, or that alt. I would call mechman. They are awesome over there.