Jeep Garage  - Jeep Forum banner

Charging System Light

16K views 26 replies 9 participants last post by  Deserthucker 
#1 ·
On Page 169 of the Manual there is mention of a Charging System Light ( a battery symbol) which should come on briefly at turn on. I have never seen this light in 6mths, has anyone seen this symbol ,maybe I have a blowen bulb.

Tony
 
#3 ·
That is insane.
So the alternator can fail and the is NO WARNING WHATSOEVER, that is pathetic.
Great way to find the battery dead.
 
#4 ·
I'd be interested to see him run the battery down to failure. There is nothing in this video to prove the system doesn't work. The battery wouldn't have lost much voltage, if any, during the time the vehicle was running.
 
#6 · (Edited)
I agree it's not a light that lights up when the alternator is not charging like my old kingswood but i believe things are far more advanced these days. I doubt the alternator is charging 100% of the time in the interests of fuel economy. So a light showing a drop in output of the alternator wouldnt actually help. When battery drops voltage or when a clutch engages on the alternator with no response it could still light up to provide sufficient warning. My point is this video is not providing the whole story. I haven't bothered to go right into it but it appears there IS a battery light and one might assume it will light up at some stage. Until someone conclusively proves the system is flawed I'm sceptical.
 
#14 ·
The reconfigurable tell tale are the two lights on the bottom left of the EVIC display, on the left, red and in the centre, amber. When you start the car they both come on. The red display on mine is the electronic throttle warning. It looks like the old school choke symbol. The light is a digital display able to present a number of different warnings (reconfigurable as opposed to fixed (unreconfigurable) bulbs lighting up an image such as the park brake symbol). if you have a red light displaying something when you start your car then the light is working.

The red warning light at the bottom left of the EVIC is where the charging light should display when needed.

This takes me back to my original comment, until proven otherwise I believe the system will work correctly. If someone can be bothered to remove the serpentine belt and run the battery towards failure, I believe the charging warning will come on. How long before that battery runs out of charge remains to be seen.
 
#15 ·
So, if Mendo is correct, the Charging Light is really a low voltage warning, and would light up if the volatge in the battery dropped below a certain point.
Still, one would have thought that it would light up to confirm the light was functional as per all the other warning lights.
 
#19 ·
When I was a mechanic, it was handy to know when the alternator was not charging.
If the idiot light only comes on with low voltage then it has already failed, as there is not much you can do except grind to a halt.
I'm not saying it is a low voltage warning

Here's the extent of my limited knowledge, I know the alternator on my 1978 Kingswood was charging the battery all the time. I know the alternator on my 2004 Falcon is not charging the battery all the time (in the interests of fuel economy). I assume the alternator on the Jeep is even more complex.

I am not convinced the system is broken because it failed to notice the alternator was not charging after only a very short period of time. IMO old mate did not run the engine long enough for the required drop in voltage (or time period) to engage the clutch/ switch for the system then to realise its not charging.

Someone more mechanically minded might be able to provide further info.

Attached more commentary re light www.jeepgarage.org/showthread.php?t=22670&highlight=Charging+light&page=1

And this one should clear up any concerns.... http://www.jeepgarage.org/showthread.php?t=12628&highlight=Charging+light

Remember just because its on the internet its not always true.
 
#16 ·
When I was a mechanic, it was handy to know when the alternator was not charging.
If the idiot light only comes on with low voltage then it has already failed, as there is not much you can do except grind to a halt. It would be much more practical if the light did what every other cars charging light does and that is warn you that the system is not charging. This could result in not using accessories like Aircon or radio to eek out a bit more distance if you are far from a service center.
I cannot believe that Jeep with so much experience building cars would have such a massive oversight.
 
#20 ·
Its not like the old times.

Due to fuel economy nowadays the alternator is charging depending on the status of the battery. If its charged, no alternator activity. If you have energy excess, eg downhill or braking, the alternator is "fired up" and starts charging. If the battery is drained, it starts charging on engine energy. If you need full engine power for acceleration, the alternator is disabled. Thus pretty complex alogarythms...

Thus, the good old idiot light does not work any more, so we are at one point more dependent on a piece of hopefully working software. Usually the system starts to behave erratic on low voltage, due to the advanced energy management the cars operate a long time even on dying batteries, wich then surprisingly cease to work on a single cold morning...

Happy Day

Achim
 
#21 ·
A quick way to confirm if it's charging is put a multimeter across the battery terminals and see if the voltage rises when the engine is running.

I would expect that the alternator will charge straight after an engine start, as that's when the heaviest drain on a battery occurs. Especially from cold.
 
#22 ·
The thing is:

The old idiot light was indicating the current wich charged the battery. Once the current stalled, you have had an immediate information that the alternator stopped charging, leaving you sometime to drive on the residual power of the battery.

The new systems seem to monitor the voltage. Thus you get the information when the voltage is already too low, so no more residual reaction time.

And the advanced starting management of the engine gets you the thing running even on an almost dead battery, since usually the engine starts after 1-2 cranks.

Happy Day

Achim
 
#23 ·
I think what is being said:
The modern cars have smart alternators and will not continally charge like the old school ones. The video only shows a short time with the belt disconnected and would possibly not be enough time for there to be any voltage drop. If the guy on the video loaded up the system with lights and HVAC it would draw down enough to trigger the system to put the charge light on.
 
#24 ·
But alternators never charged all the time unless the regulator was faulty. Regulators have been used for ever so they do not overcharge batteries.

I'm going to experiment when I get mine and see if I can make it ight up.

The test in the video was too simplistic however, I agree on that. Having an engine idle for a few minutes is not a significant load once it's started.
 
#25 ·
I don't know about this smart alternator.
Since the charging update I have been monitoring the voltage while driving.
I am only seeing .2v deviation. 14.2v to 14.4v using a OBDII monitor.
If it was to go into a no charge state say under full acceleration the voltage should drop.
I tried this yesterday after the car was sitting for most of the day in the sun fridge running of the second battery takes about an hour to get it back to charged state. and charges at the same time as the car battery. So we got a full load on the alternator. Under full acceleration voltage did not change.
4 hours later running at 110kmh for that time. Tried again no variation.
My conclusion is the alternator will charge when it sees the battery needs it and floats at 14.4v. and will maintain that up hill down hill full acceleration full engine braking. After all we are not driving a hybrid.
Stop your car and just turn on the ignition check the voltage it will drop rather fast to 12.6v and then hold there.
If the alternator was to go into a non charge state or limp mode I would expect to see 13.8 volts or lower, but this has not been the state.
 
#26 ·
Hey Deserthucker

What OBDII meter do you have? I have a Scangauge II sitting in my top drawer that I used to have in the Jackaroo. I'm waiting to see if it works in GC as the Scangauge is supposed to support CAN and EOBD.
 
#27 ·
I have a scangauge II permanently mounted on top of the steering column.
and borrow my mates PRO OBDII starscan with Detroit diesel software.
Gives you the basics but not the jeep stuff.
Would love to get hold of the jeep software for it.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top