Jeep charging system

[mrloboy]

My son's daily driver is a '98 Jeep Grande Cherokee Limited with a 5.2 litre engine. While driving, the voltage will either drop to 9 volts  quickly or gradually and the information center announces  "Dead Battery" If he shuts the vehicle off and restarts it goes right back to charging 14.3 volts. Testing the output of the alternator reeds the same and a load test shows the battery is also good. Could it be the brushes are close to shot or? Anyone have an idea what to look for? Thanks, Rick

[38HAULR]

I would dare say the reg would be suss aside from a poor connectionto the alternator Rick.  By all means check the brushes.  The way I look at it, once the brushes are worn things do not get better , deteriorated  operation  will stay bad.
What is the config of the alternator?  There are those , Bosch for example that have the regulator  and brush holder as one unit.

Frank.

[wayne petty]

a few things... these are nippondenso units.. at least the ones with the tin cover on the back...

the computer controls the alternator...

can you verify the charging voltage... set a digital volt meter to 20 volts DC scale...   test at the battery...  you should have over 14.1 volts.. but probably closer to 14.8... with the engine running..


i take it that you are handy with tools being on this forum..
you can remove the alternator from the engine.. lay it on the work bench... the brushes and the rectifier bridge  all come out..

the brushes are soldered into the brush holder.. but you can get replacement brushes and with care solder them in...

the rectifier bridges also come off.. there are several screws in from the outside where the stator windings attach.... once you have the rectifier bridge off...   examine the solder joints carefully... i have found a Lot.. that just had a few bad solder joints..  a few minutes with a solder tip. and some ROSIN CORE solder... and its fixed...

post the part numbers off the alternator .. you can order parts directly from wagner alternator that i posted a few days ago...

or complete units are available..

if you have ever torn down a delco internally regulated alternator. these are easier.. as you only have to remove the rear cover..  everything important except the bearings is external...

please use a volt meter for testing.. DO NOT PULL A CABLE to test.. you will damage the alternator...    diodes are also cheep...  as are brushes..

[wayne petty]

oh... when voltages drop like is displayed on the cluster...

test the voltage at the  battery with your digital volt meter and the engine running like i said above..  turn on as many lights as possible..

you need to verify that you don't just have a bad connection...


the problem could also be in the main computer or power control module ..

verify first...

[mrloboy]

oh... when voltages drop like is displayed on the cluster...

test the voltage at the  battery with your digital volt meter and the engine running like i said above..  turn on as many lights as possible..

you need to verify that you don't just have a bad connection...


the problem could also be in the main computer or power control module ..

verify first...

Thanks Wayne. I will go through the system as you described. The only alternator experience I have is with Delco units. Time to try something new! Rick.

[38HAULR]

Also if this is a "sense" type set up with a sense wire going to the battery,this is usually a  light gauge wire fused at the battery end.
If this connection is poor you can get erratic charging.

I was once caught up with my son in laws vehicle "no charge".
I swapped it out for him after purchasing a replacement. Still had probs,this I found to be a corroded sense wire at the battery terminal end . my first encouter of the sense wire:oops:  :oops:  :oops:  :oops: .

The bonus was, that the replacement I bought was a new 80AMP unit I was fortunate to find  from a wreck.  By swapping the serpentine pulley to a vee belt,I now have a good alternator for my Chev  for $30.      

[wayne petty]

the upper left corner is the wiring diagram for the alternator for the 97 models..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/0a/9e/18/large/0900c152800a9e18.gif

here is a more complete wiring diagram for the engine controls...

the alternator is in the upper right..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/0a/9e/13/large/0900c152800a9e13.gif



here are the trouble shooting pages for the alternator/charging system

http://www.autozone.com:80/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c152800a98a2


check your P messages...

[1800guy]

Don't forget - when checking voltages that the alternator must be well grounded.  You should have nearly the same battery voltage reading grounding your meter at the battery or on the alternator case.  Usually not a problem so it's easy to overlook (or forget - ask me how I know)  :oops:

[38HAULR]

Don't forget - when checking voltages that the alternator must be well grounded.  You should have nearly the same battery voltage reading grounding your meter at the battery or on the alternator case.  Usually not a problem so it's easy to overlook (or forget - ask me how I know)  :oops:

You can get a burnt finger. :oops:  :oops:  :oops: .
Had this issue when doing an engine swap into my wifes vehicle.
Not charging was found when all fired up for testing.
It transpired that the alternator was affixed to the aircon compressor bracketry that is shock mounted via rubber grommets through the bolt holes.
The ground strap was missing.  
I had my wife increase the rpm,s as I probed around ,vehicle had all accys on.
I had some hook up wire anchored to the batt negative terminal ,the other end I pressed to the alternator housing  using my finger.
Almost left a hole in it :cry:  :cry:  :cry:  :cry:  :cry:
I apologised for the colourful language. :oops:  :oops:  :oops:
Frank.

[1800guy]

I have found that painful lessons seem to soak in quicker - most of the mistakes I repeat are the ones that cost nothing