Alternator or Battery?

[Pavoner]

I have a 1994 4.0 L 4x4 ranger. I have been having some electrical problems of late. First of all at high iddle(1500 rpm) my voltmeter(on dash) shows about 14v. That looks good to me, but once the engine warms and the iddle switches to 800-1000 rpm I show approx 11-12v the lights dim etc. I recently had trouble starting my truck in a huge cold snap we had about three weeks ago. My battery was dead, I mean DEAD! no click no nothing. got it fired by boosting, then put my charger on it overnight. Next day started truck and let it run for about 20 mins with heater on 3/4(nothing else on), I stalled it backing out of the drive way and it didn't have enough juice to turn over even with the engine warm... Just wondering if a weak/dying battery could be responsible for this or should I be looking harder at my alternator. It's the voltage drop that causes me concern about the alt... the battery I would not be shocked about having to replace as it is pretty old.


Thnx for your time guys sorry for the long post.

 

[COPPERHEAD85]

this is not a error proof way to check the alt but its the simple way to get an idea if its charging or not.........
check the voltage at the battery with the engine running with a simple volt meter.if it reads 13.5 or better,alts. probably good and your batterys toast.
you can go to the zone and have it checked but heres a little tip for all you guys.....
that high dollar rig that they hook to your battery to check it also a ...."selling tool"... if you get my drift

 

[MAKG]

Yup, and FYI, it's normal for almost any charging system to brown out some at low-idle. You measure charging at 2000 RPM.