96-97 Dodge Caravan Charging problems-Alternator ?

Messages
9,808
Location
New Jersey
This vehicle is in Florida and i am here in NJ it belongs to a friend of my sisters. He called me this morning and said his alternator light comes on after about 1 minute and his battery is not charging (He said he tested it with a volt meter) so i told him since his battery is only about 6 months old it sounds like the alternator so him and a friend took the old alternator out and took it to an auto parts store (maybe Auto Zone) and they put it on their alternator machine and said it passes all the tests and the unit looks good. I told him a few minutes ago that he should replace it anyway because the test they did was only about 30 seconds and maybe the test was not long enough.. He thinks the alternator is original with over 140,000 miles on it. Anyone agree with me or am i missing something and if so any ideas? Im not sure if it is a 96 or a 97 but it is a 3.3 according to him.
 
Messages
8,098
Location
MI
Lots of things to check before replacing an alternator that tests good. The main wire between the alternator and battery might be bad and/or have a blown fuse or fuseable link. The alternator field wires between the alternator and PCM could also have gone bad, i.e. - rubbed through or broken.
 
Messages
214
Location
WA
First thing to do is check all fuses. Then clean all major wires coming from the alternator, battery and ground straps.
 
Messages
214
Location
winter park, Fl.
Ha...! OK, it is the alternator, a few months ago I had the same issue with a 2000 Caravan (same 3rd. generation) took the alternator to Autozone and checked 100% perfect, then took it to Advance Auto Parts passed with flying colors, then me been me I opened the alternator and none of the brushes were touching the slip rings, in other words "double failure" just one is enough to shut it off. 140K. miles is just the usual mileage in a V6, mine lasted 200K but it was in a 4 cyl. where it is in a cooler place and a little less demand. Other thing, this alternators don't have an internal voltage regulator like most others, it is controlled by the PCM (engine computer) the auto parts places don't have a clue about most things. Ask them to look for an alternator/starter rebuilding place, call them to ask if they can replace the alternator, they will have a competitive price and a much better quality replacement, tell them to replace it with a 125A, alternator if it doesn't have one already, they are a direct replacement and the wiring is set to use them, they were an option in all the trim levels of these vans.. Also, did I mention I'm in Florida too?, best of luck, I don't like to do remote troubleshooting but sometimes it is what it is.
 
Messages
215
Location
AZ
I was told my alternator was ok.And it wasnt.Check and make sure you have a good ground.And with that amount of miles? Maybe a new alternator is a good idea.
 
Messages
17,501
Location
Clovis, CA
<span style="font-family: 'Verdana'">The voltage across your battery terminals should go up a little bit after starting the engine if the alternator is charging like it should. The voltage should go up about two volts into the 14V range.</span>
 
Messages
2,191
Location
VA
I don't agree with you. You tell them to take off the alternator and get it tested. It tests good and your advice is to replace it any way because?? Then come here and ask for opinions of your 1000 mile diagnosis? Maybe they need to take it to a shop... or another friend who can look at it instead of you throwing out ideas having no idea whats going on. Alternators don't normally just quit working because they have a certain amount of miles on them and that is not a lot of miles. Number one killer of an alternator is a bad bearing, not a charging issue.
 

crazyoildude

Thread starter
Messages
9,808
Location
New Jersey
actually i said it sounds like the alternator i never said have it tested but they did and being in the engine business all my life i have seen bad alternators pass with flying colors. It's just a hunch but since he has no money and we are helping him pay for it i think i made the right choice but only time will tell. He looked at the wiring as best as he could and it looked good to them next i will send him a pcm if that don't work he can send it back to me. I feel bad for this guy he has no luck and is always the victim but tries to help everybody. I believe the regulator is in the pcm but im not 100% sure on that one.
 
Messages
17,501
Location
Clovis, CA
crazyoildude, There's a real good PDF that Fluke puts out called the "beatbook." It tells you how to test an alternator with a multimeter. It would easier for me to send it you than to try to find the link. PM me your e-mail address.
 
Messages
5,091
Location
USA
All EFI Chrysler engines have the regulator in the computer.Some Cummins diesel early models were external though.This is a good case for a Scan GaugeII.You can watch the voltage to the tenth of a volt.
 
Messages
214
Location
winter park, Fl.
Originally Posted By: bvance554
I don't agree with you. You tell them to take off the alternator and get it tested. It tests good and your advice is to replace it any way because?? Then come here and ask for opinions of your 1000 mile diagnosis? Maybe they need to take it to a shop... or another friend who can look at it instead of you throwing out ideas having no idea whats going on. Alternators don't normally just quit working because they have a certain amount of miles on them and that is not a lot of miles. Number one killer of an alternator is a bad bearing, not a charging issue.
The Nippondenso series 121000-xxxx is known for very long lasting bearings it is used not only by Chrysler but by a lot of other manufacturers, Toyota been the biggest, it is normal for them to wear the slip rings and brushes well before the bearings, many times you can change the brushes and get another 100K miles from them and the bearings will still be good, you don't even have to dismantle the whole alternator, just take off 3 10mm nuts the positive post nut and perhaps another 10mm nut sometimes you don't. then the dust cover will come off and have access to the brushes, slip rings, rectifier bridge and regulator if it uses one, it takes minutes to check that. In the old days of Delco alternators with their undersize bearings sure the bearings did go off long before the rest but nowadays specially with Japanese alternators that is hardly the case with their properly size bearings. To the OP, the 90A. alternator for this vans carry the Mopar part #: 4727220 and Nippondenso (Denso)#: 121000-3521 the 125A alternator Mopar #: 4727325AA and Denso#: 121000-4330. Like I said before, the 125A will fit in place of the 90A. and the wiring is the same for both the difference in use is huge. As I write this I'm in the process of adapting a Denso hairpin alternator to our van but that is another story. Where is Florida are them? if in the Orlando area there is a place called TRS in Silverstar road, I buy my parts from them when in a pinch, they do repairs there and work on Saturdays at least they did few years ago
 
Messages
36,516
Location
ME
Originally Posted By: NHGUY
All EFI Chrysler engines have the regulator in the computer.Some Cummins diesel early models were external though.This is a good case for a Scan GaugeII.You can watch the voltage to the tenth of a volt.
Yeah this! There's usually a way to ground the field on the car so it goes 100% charging, like sticking a paper clip through a hole somewhere. This would say the alt is good but the computer controls wonky. These computer controls go wonky all the time. There should be an OBD code for this issue too.
 
Messages
1,769
Location
Toronto Canada
I have had a 96 + 98 and now a 99 Dodge Caravan. I have seen the brushes wear out with mileage. They then become intermittent. Working sometimes and other times not. They usually test well but won't keep a battery charged. I have a spare one in my basement. If he was here, he could have it. Must be a dime a dozen at the wreckers. I have no idea if this is his problem, but if the wiring looks good and I thought the battery was good, I wouldn't hesitate to replace the alternator.
 
Messages
214
Location
winter park, Fl.
Originally Posted By: NHGUY
All EFI Chrysler engines have the regulator in the computer.
That is correct. Also IIRC with headlights, A/C and rear window defroster on the idle voltage should be above 14V. I'll have to check that with the FSM if you want me to.
 
Messages
214
Location
winter park, Fl.
Originally Posted By: eljefino
Originally Posted By: NHGUY
All EFI Chrysler engines have the regulator in the computer.Some Cummins diesel early models were external though.This is a good case for a Scan GaugeII.You can watch the voltage to the tenth of a volt.
Yeah this! There's usually a way to ground the field on the car so it goes 100% charging, like sticking a paper clip through a hole somewhere. This would say the alt is good but the computer controls wonky. These computer controls go wonky all the time. There should be an OBD code for this issue too.
No hole to ground the field in these alternators, there is and OBD code for the computer going "wonky" and the PCM's seldom go bad in these cars unless you short something to positive.
 
Messages
9,559
Location
Boston, MA
Originally Posted By: mene
Originally Posted By: NHGUY
All EFI Chrysler engines have the regulator in the computer.
That is correct. Also IIRC with headlights, A/C and rear window defroster on the idle voltage should be above 14V. I'll have to check that with the FSM if you want me to.
And the alternator will test good at the store because the regulator is still back in the ECU in the car. An on the car load test is needed, just measuring charge voltage with little or no load can be misleading. Brushes not touching the slip rings should cause a fail even with the in store tester and worn brushes starting to lose contact will behave just as a prior poster indicated. Denso alternators are very good quality unless the unit has already been rebuilt once. Often rebuilders don't true the rotor slip rings and the replacement brushes they install wear quickly.
 
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Messages
3,888
Location
southern mo
Check alternator fuse and b+ wire leaving alternator. Check battery connectuons and belt condition and tension. Replacing an alternator that passes is a foolish thing to do honestly.
 

crazyoildude

Thread starter
Messages
9,808
Location
New Jersey
He is not great with fixing cars he is ok but says his friend is pretty good, my thinking is if it's not the alternator it may be the ecm i told him i believe its on the drivers side but im hoping its the alternator. Im pretty sure if he even finds a good ecm it has to be programmed and he will have to take it somewhere for that anyway. He did say the wires that plug into the back looked a little corroded so who knows he is far away.
 
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