As some of you know, I'm fighting my low rpm and stalling issue, went to check the battery while running off the terminal points and read 13.67 while running, and when it was off it read 12.67. Is my alternator charging enough? I noticed with my dash lights on they would brighten up a bit when I hit the gas peddle. Also I hear a little whistle on accel which I hear is a sign of the alternator going out
Is my alternator under charging?
- Thread starter D M
- Start date
Your battery is fully charged with that 12.67v reading. When the battery is fully charged the alternator doesn't put out much voltage so that measurement seems about right.
Even though the voltage numbers appear good; it couldn't hurt the check the following connections to ensure they are clean and tight: positive on the starter, grounds on the block near the oil filter, ground that is bolted to the center of the firewall, ground on the battery, positive on the battery, positive charging stud on the alternator, the field connections on the alternator.
Does the voltage significantly change when you add load? For example, if you turn the brights and the fog lights (and any other resistive loads) on, does the voltage drop?
A properly functioning alternator should be able to maintain a consistent voltage with all of those accessories on even at idle.
If it does drop, either the alternator is failing or the alternator is insufficiently sized for the loads.
Go to any auto parts store and they will test the alternator in the vehicle for free. The alternator test measures the ripple current (essentially the fluctuation in output current due to the rectification of AC current to DC) on the alternator to see if one of the three phases is dead.
A properly functioning alternator should be able to maintain a consistent voltage with all of those accessories on even at idle.
If it does drop, either the alternator is failing or the alternator is insufficiently sized for the loads.
Go to any auto parts store and they will test the alternator in the vehicle for free. The alternator test measures the ripple current (essentially the fluctuation in output current due to the rectification of AC current to DC) on the alternator to see if one of the three phases is dead.
I did a bunch of alternator testing with my LJR after I got it. Previous owner had an aftermarket stereo system installed; it needed wired correctly so I have a stereo shop fix all the wiring. After, I notice that at night with stereo on and lights etc I would have a faint whining sound. The factory alternator would only measure 13.3v at idle and maybe 13.4-13.5 while driving. Had a jeep shop check my charging system and came back with no issues, but still had the whining sound. I swapped out the alternator for the durango one and that fixed my problem. At idle I would get 13.5 - 13.6v. Whine is no longer there either. I've never seen my volts at 14 which I know a lot of other jeeps run at. Also my jeep doesn't have a battery temp sensor; a lot of people found this strange and almost didn't believe me that i didn't have one.
I too have the temperature sensor in the bottom of the battery tray. My charge voltage when cold has been as high as 14.5 when sitting for a few weeks. Generally when started daily, but cold in the morning; the charge voltage is 14.1 and drops quickly to 13.9. I have heard that the later model TJs (>04) do not have the temperature sensors to sense battery temperature.
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