Alternator not charging at idle

[Drunner97]

i dont know if you have upgraded to a higher amp alternator yet, but it do require a shorter belt.



GATES K070825HD



im using this belt now since my alternator has a smaller pulley. also my voltage dips to the low 12.5 when my rpm is at 500, so it dosent charge at that low, these alternator like to see 800.



i think there is a 3 to 1 ratio for rpm calculation they used.

I'm running the shorter belt. Standard charge is 650ish. It's on a relay or something that activates charging 650+ rpm you would have to bypass the stock wiring or figure out which relay activates the charging via amperage.

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[riceandpho]

I'm running the shorter belt. Standard charge is 650ish. It's on a relay or something that activates charging 650+ rpm you would have to bypass the stock wiring or figure out which relay activates the charging via amperage.

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How's the auto tensioner. Sometimes they start loosing tension. I have the same simptons when my truck is in gear and I'm on a stand still. Voltage drops low enough.

 

[blackoutt]

Colder this morning so the idle was up at 650rpm. I also have an alt-s diode but this should be plenty good at idle. I must have caught it warmed up with lights on yesterday to see it in the mid 12.x's

 

[ZiaMan]

Have you tried disabling the dual battery set up and going back to stock single battery to see if the dual set up is causing the idle/charging issue?

 

[Drunner97]

How's the auto tensioner. Sometimes they start loosing tension. I have the same simptons when my truck is in gear and I'm on a stand still. Voltage drops low enough.

Nope, belt is still pretty tight. I'm convinced it's in the electrical system somewhere that's causing the ECU to change the RPMs.

Colder this morning so the idle was up at 650rpm. I also have an alt-s diode but this should be plenty good at idle. I must have caught it warmed up with lights on yesterday to see it in the mid 12.x's

At least you know your alternator is working. I'm still wondering if you can override the ECU with techstream and set a hard idle parameter.

Have you tried disabling the dual battery set up and going back to stock single battery to see if the dual set up is causing the idle/charging issue?

To a degree. I have a basic dual battery setup on a switch that lets me connect/isolate them. Whenever I reset my idle I keep them isolated and it typically idles correctly until connect the batteries for charging. I tend to run into the issue with the house battery has been drained down after sitting for awhile since I don't drive the 4runner daily.