[Waterman2112]

Any ideas around alternator intermittences…?

Some slow cranking issues… had the original battery. Thought it was time.. checked alternator output and checked with Vector unit.. all seemed good.
No light on the dash with regards to charging..

New battery lasted for 6 months or so… then slow cranking again. No light on dash. The photos show the Vector charging unit hooked up.. about 14.5 volts and about 15 amps or so… used “alt check” function and diagnostic read was “good.”

Is it possible that the alternator is cutting off when hot or some other issue causing intermittent function..? Is there some other diagnostic route I should employ..?

[Captain Planet]

Parasitic load draining the battery?

Check the battery voltage with a multimeter at night, then again in the morning.

Maybe clean the terminals.

I had an alternator go at about 70k on mine, dealer covered it and the battery under warranty. Wasn't slow cranking though.

See if you can see/hear arcing in the alternator when it's running.

[fkheath]

Originally Posted by Waterman2112

Any ideas around alternator intermittences…?

Some slow cranking issues… had the original battery. Thought it was time.. checked alternator output and checked with Vector unit.. all seemed good.
No light on the dash with regards to charging..

New battery lasted for 6 months or so… then slow cranking again. No light on dash. The photos show the Vector charging unit hooked up.. about 14.5 volts and about 15 amps or so… used “alt check” function and diagnostic read was “good.”

Is it possible that the alternator is cutting off when hot or some other issue causing intermittent function..? Is there some other diagnostic route I should employ..?

Forget the alternator, it is good. Your problem is the battery.

What is the battery voltage just prior to trying to start the car? It should be 12 volts or a bit more. If less, either something is draining the battery, or the battery is not keeping a charge.

Suggest you get one of those cheap digital voltage displays that plug into the 12 volt outlet. That will show the battery voltage anytime the car is on. If you really have an intermittent alternator, that will show immediately on that voltage display as something below the nominal 14 charging voltage.

Just keep in mind that any voltage over the resting voltage of the battery will still charge the battery.

[Waterman2112]

I rechecked when the vehicle was at operating temperature… plugged the Vector charger up and rechecked with the alternator diagnostic button… it showed “alt good” then went back to battery voltage with the vehicle still running… it showed 14.7 volts and 15.5 amps.. THEN.. right then and there the amp screen went blank.. pushing again on the voltage button the volts were 13.5 volts (if you push that button again it toggles to amps)… NO amps displayed.. it didn’t even say zero amps.. it just didn’t display anything for amps…. Then hit the alternator test button.. it displayed a blinking alt icon and a triangle with a (!) in the middle of it… bad alternator…

So it seems my alternator is working some of the time but probably not working most of the time… weird… I guess that’s the way they fail..? Intermittent… then complete…? Probably so..

I checked out a couple of YouTube videos on changing the alternator… seems straightforward with some tight bolts on a back bracket assembly… the last 8 numbers on my VIN say it’s a 130amp type (2 choices for the Runner it seems at 100amp and 130amp) probably a good time to change the serpentine belt..

Just want to see if I was missing something… Any advice on additional checks are very much appreciated.