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Grand Cherokee 2013 electrical problems

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Discussion starter · #21 ·
Hi Coldcase,

I don't know where these indicated points are?

JKPROPERTIES said:
How would I go about checking this?
Click to expand...
There is no internal regulator so the generator could read 24v at the generator fused b+ connector when its disconnected from the vehicle. What voltage is displayed in the EVIC vehicle information screen? If the PCM is seeing 24v at C1 Pin 24 and you are still seeing full field voltage from the PCM at the generator field control pin, then its probably a bad PCM (or connection). It should cut the field voltage (it adjusts the DC signal with PCM) if the voltage is above the set point.
 
Discussion starter · #22 ·
ColdCase said:
Just saying that you can do more troubleshooting to be sure its the alternator, if you want. Or you can just start swapping parts. Someone checked the battery and alternator, the only thing left is the regulator and wiring and belt (is it slipping?). The regulator is in the PCM, so you could check that before swapping parts, if you want.

These computer controlled vehicles don't act like old school stuff. The windows and roof modules, many others, will shut off when when supplied with over voltage or under voltage.... each is a separate computer and each has their own set points. Some will set a DTC fault, some won't.

Forum sponsor rockauto sells reman alternators from Remy, Pure Energy, AC Delco, and MOPAR. Dunno about availability in SA, but most parts stores should have remanufactured if not new generators. Some may provide rebuild services, to rebuild the one you have.

https://www.rockauto.com/en/catalog...jeep,2013,grand+cherokee,5.7l+v8,1504697,electrical,alternator+/+generator,2412

24VDC is a lot of volts to put on the Jeep's electrical system. If the battery bus is indeed running more than 15VDC you are heading toward damaged batteries and blown bulbs.
Click to expand...
I really do want to find the problem and not just start swapping parts, sorry if my lack of understanding what you are saying comes across as if I don't want to take your advice...
 
Discussion starter · #23 ·
JKPROPERTIES said:
Hi Coldcase,

I don't know where these indicated points are?

There is no internal regulator so the generator could read 24v at the generator fused b+ connector when its disconnected from the vehicle. What voltage is displayed in the EVIC vehicle information screen? If the PCM is seeing 24v at C1 Pin 24 and you are still seeing full field voltage from the PCM at the generator field control pin, then its probably a bad PCM (or connection). It should cut the field voltage (it adjusts the DC signal with PCM) if the voltage is above the set point.
Click to expand...
Is the pcm something I can check myself?
 
#24 ·
Its hard to diagnose and explain over the internet. There are some wikis and description sites that may help you. You need to be familiar with batteries, alternators, probing of wires, connectors, circuits to be able to do much.

You can replace batteries and alternators on your own. Replacing the PCM requires a DTC test set (dealer) that can write your VIN and mileage. You should be able to buy one with your VIN and mileage programed for you.

If you are seeing the same symptoms as before and the alternator replacement fixed it, there is a decent chance another alternator will also fix it. Shops generally replace a PCM if they suspect it. The regulator circuit is one of those gray areas.
 
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Discussion starter · #25 ·
I have spoken to the guy that services my vehicle, he says he really doubts that the Alternator is the culprit and said he would suspect the PCM, but I need to bring the car in so he can check, I don't trust any of the dealers/mechanics had bad experiences since I have had cars, they tend to just rip me off,
New PCM around $1000 used/refurbished $400 plus about $100 to program.

I have found some local guys that say they can test and fix a faulty PCM/ECU. $20 to test, around $110 to fix subject to fault, and also around $100 to program.
Is it worth fixing a PCM in your experience?
 
Discussion starter · #27 ·
HI Coldcase,
I have taken the PCM to a company that claims to test them, they said before testing there is a misunderstanding, the regulator is still in the alternator, but is controlled from the PCM, because if the regulator was in the PCM there would be cables from the alternator going to the PCM, I think this makes sense? They tested and said no fault found.

They insist it is the alternator's regulator.

The mechanic disagrees, says the PCM cannot be tested out of the vehicle... I don't know.
He wants to charge me to test the vehicle and even if it is the alternator i will still pay for this test... I feel this is an ethics problem and I am being ripped off.

What are your thoughts?
 
#28 ·
Most cars have a regulator in the alternator. The Jeep, at least one of your vintage, is one of the few that is different. See the description of how it works earlier in the thread.

There is a cable from the alternator to the PCM as shown in the circuit diagram posted earlier. It contains a sense wire, for the PCM to determine what the voltage is, and a field wire to control the alternator output.
 
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Discussion starter · #29 ·
So, I went to see alternator guys today, that have fixed a bunch of alternators for these vehicles, the alternator does in deed have a "regulator" but not the same as older cars regulators, they will charge me $200 to remove, fix and fit the alternator.

They also fix alternators that don't charge, apparently an Italian pirate part that is better than the original.
I am collecting the vehicle tomorrow, will let you know if this has solved the problem.
 
Discussion starter · #30 ·
ColdCase said:
Most cars have a regulator in the alternator. The Jeep, at least one of your vintage, is one of the few that is different. See the description of how it works earlier in the thread.

There is a cable from the alternator to the PCM as shown in the circuit diagram posted earlier. It contains a sense wire, for the PCM to determine what the voltage is, and a field wire to control the alternator output.
Click to expand...
Hi Coldcase,
Thank you for your reply, I am not a car guy, so I am only writing what the feedback is I am getting back from the relevant guys that work on these things.
I am getting told 2 things:

1)PCM has the regulator built in and no regulator in the alternator.
2)PCM controls the regulator in the alternator.
 
#31 ·
I would take the relevant advise but do you know how these relevant guys explain their discrepancies with the factory service manual info posted earlier? Wouldn't you think the factory knows how things are put together? Those that know Jeeps well, know about #1. Other techs assume #2 as that is the usual case for other makes an models.

FCA/Jeep does it this way so they can cut the alternator drag when you apply a lot of throttle, gives you a few more ponies. Also can help meet EPA mileage goals in some cases as the amount of drag can be software controlled in a variable manner. i.e. a little less drag when accelerating, more drag when braking. There are a couple ways to skin that cat.

I'm not aware of any differences for the export market in this case, but exports could be different.
 
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Discussion starter · #32 ·
ColdCase said:
FCA/Jeep does it this way so they can cut the alternator drag when you apply a lot of throttle, gives you a few more ponies.
Click to expand...
The guy that tested the PCM explained this to me, but said there was something in the alternator(maybe he said regulator) for ease of explanation.

I just got a call from the alternator guys, they say all looks good, I can come fetch the vehicle, I have asked them if they can give me a photo of the replaced part or a correct description of it.
I will update as soon as I can.
 
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JKPROPERTIES
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