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Jeep GC 2014
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Discussion Starter · #1 · (Edited)
hi
I got a used GC 2014 ....original voltage (on the car screen) was 15 always.

last year, I went ahead and changed the battery, voltage drops to 14.

a year later Voltage goes down to 11....I put another new battery!
problem continues, so I took it to the dealer who said the alternator was reading about 12.5v and changes the alternator.

a month later, the voltage is down again down to 9 this time. it jumps up and down.

Voltage seems to be at its lowest on a cold start ...gets higher to 13/14 Volts after a few seconds of driving....

any ideas?
 

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Jeep GC 2014
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Discussion Starter · #2 ·
I forgot to mention: I noticed the red battery cable on the fuse box is melting the plastic all over the place! please see pic....not sure if this is related?
I have had an upgrade HID harness on this car for close to a year and never had any issues before.....
 

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Lifer: Old Geezer
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That should not happen.
And if the dealer didn't notice it, try finding a dealer with a pulse and at least two active brain cells. You MIGHT want to try an electrical specialist.
Is that cable at all loose, you might want to pull it, clean the hell out of it, and put it back with a good tight fitting as a loose cable connect can cause local heating.

Just hope it isn't the voltage regulator part of your computer.
 

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Discussion Starter · #4 ·
That should not happen.
And if the dealer didn't notice it, try finding a dealer with a pulse and at least two active brain cells. You MIGHT want to try an electrical specialist.
Is that cable at all loose, you might want to pull it, clean the hell out of it, and put it back with a good tight fitting as a loose cable connect can cause local heating.

Just hope it isn't the voltage regulator part of your computer.
thanks for the help....yes, it was loose!
I just cleaned it up then tightened it....now voltage is a solid 14 with very little change to 13 or 15....
I just cannot believe I got ripped off by the dealer over a loose screw!....that new alternator didn't do a thing!
 

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Lifer: Old Geezer
Overland
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thanks for the help....yes, it was loose!
I just cleaned it up then tightened it....now voltage is a solid 14 with very little change to 13 or 15....
I just cannot believe I got ripped off by the dealer over a loose screw!....that new alternator didn't do a thing!
Tip: A cheap digital VOM can save a dealer/repair fee.
I would suggest getting one with long leads and the ones with needle tip leads allow you to poke into wires without damaging them, but a $10 special is more than good enough.

Very common is loose grounds, where again just removing and cleaning and tightening the main ground from the alternator/battery to the body is highly recommended..

But with the VOM, you can check voltages at each point, spot bad cables, etc.
 

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Grand Cherokee
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The PCM will change the charging system voltage according to conditions, usually temperature.

15V is too high, althoug 15.0V isn't that high, in cold weather I have seen 14.8-14.9V.

When the battery is fully charged the voltage of the charging system usually drops. But it should be above 13.8 volts.

The float voltage of the battery is 13.5-13.75 volts, you need to apply a higher voltage than that to get the battery to charge.

The red battery light goes off for three reasons, but it means there is an electrical problem. System Voltage to Low, System Voltage to High or a fault was detected in the alternator field control (the PCM control of the alternator).

Sorry for your experience with the Dealership, far too many bad ones out their, that don't even bother opening the Manuals they are provided that have a thorough troubleshooting guide to take them through proper troubleshooting, and instead just guss and replace parts at your expense until they luck into the solution eventually.
 

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Laredo 4x4
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All good points regarding check ecking with a voltmeter. Keep in mind that a bad connection can show good voltage during low current conditions. During higher currents, the fault may show itself.
 

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All of these tests are interesting, but the melted stuff is the red flag that the mechanic should have dealt with first.


Well, that would be true if it was a mechanic that worked on it. Unfortunately, it was probably a parts-swapper. /rant
 

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i wish this was a current thread ,...i have a 2019 compas that started having charging issues ,,,took it my local shop who diagnosed a Bad Battery {{{wouldnt hold a load }}} seemed fine for first hour or so i drove it...then voltage started dropping and ended up now 2 days later at 12.9 {{{was running 14.5}} at times when i drive it it jumps to 14.5 then slowly back to 12.9 and back up again ...did this three or 4 times in a row last night so i parked it and testing everything this morning ...checked with old time analog volt meter and its shows about 13.5 the drops to about 12.5 underload but also reads charging systen isnt working ,,,so im unclear weather this is a part of the part time charging system ,,,the alternator taking a dump or something in the PCM voltage control going bad ,,,,not gonna sit there replacin partts and my dealers suck ,,,just curious where the voltage controlled IS {{{visualy }}} under the hood ?
 

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thanks for the help....yes, it was loose!
I just cleaned it up then tightened it....now voltage is a solid 14 with very little change to 13 or 15....
I just cannot believe I got ripped off by the dealer over a loose screw!....that new alternator didn't do a thing!
A good reason to try every DIY trouble shooting possible yourself before taking it into the stealership.
Before going to the stealership research the problem first so you know more than the snot nosed kid thats assigned to fix your Jeep.
Could save a lot of $$ and trouble just going to the dealership.
Some dealerships have excellent experienced techs while other not so much...a toss of the coin.
 

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A good reason to try every DIY trouble shooting possible yourself before taking it into the stealership.
Before going to the stealership research the problem first so you know more than the snot nosed kid thats assigned to fix your Jeep.
Could save a lot of $$ and trouble just going to the dealership.
Some dealerships have excellent experienced techs while other not so much...a toss of the coin.
Yup ,,,,i just went over stuff in stages ,,,step by step . seems to be either a bad voltage regulator or the control in the PCM
 

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i wish this was a current thread ,...i have a 2019 compas that started having charging issues ,,,took it my local shop who diagnosed a Bad Battery {{{wouldnt hold a load }}} seemed fine for first hour or so i drove it...then voltage started dropping and ended up now 2 days later at 12.9 {{{was running 14.5}} at times when i drive it it jumps to 14.5 then slowly back to 12.9 and back up again ...did this three or 4 times in a row last night so i parked it and testing everything this morning ...checked with old time analog volt meter and its shows about 13.5 the drops to about 12.5 underload but also reads charging systen isnt working ,,,so im unclear weather this is a part of the part time charging system ,,,the alternator taking a dump or something in the PCM voltage control going bad ,,,,not gonna sit there replacin partts and my dealers suck ,,,just curious where the voltage controlled IS {{{visualy }}} under the hood ?
Is this an AGM battery?
Was the 12.9 Volts with engine off? If so thats normal.

The alternator's voltage regulation is controlled by the PCM these days.
Far as i know there's no such thing as an auto part time charging system like with some battery tenders.
If its an AGM battery, they have a different charging curve compared to conventional lead/acid batteries.
With my '18 WK2' AGM, the engine running charging voltage does fluctuate some but never seen it go down to 12.9 VDC.
I have on occasion seen it go down into the high 13 Volt range.

For old school lead/acid batteries its normal for the charging voltage to drop a little at idle with a high electrical load.
The best way to check the charging voltage is to start the engine then turn on the headlights and HVAC blower motor on high to present an electrical load to the alternator.
No load should be around 14.7 VDC, load should not drop below much below 13.5 VDC.
If with engine running and your 12.5 Volt measurement is probably the problem keeping the battery fully charged.

Its unlikely the PCM itself is the problem, its electrical connection to the alternator yes.

Since the problem appears to be intermittent and the battery connections are ok the first things i'd check are:
-check the grounds especially the one going to the engine block

-make sure the alternator's drive belt is not slipping

-the alternator could be bad. There are shops that will test an alternator but they might be hard to find. Probably not worth the money and time to remov the alternator.

-make sure all the electrical connections on the alternator are tight with no corrosion
if your alternator has a connector pay special attention for spread pins, etc.
Caution: be extremely careful checking the alternator's output terminal, its at +Pos battery potential and if grounded accidentally = 4th of July or a trip tho the emergency room. Disconnect the battery's -Neg ground cable first before checking the alternator's electrical connections.
 

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all connections good ...belt is good ....i have a battery alternator tester i bought a few years ago and shows as of yesterday the aux battery is dead,, and alternator wasnt charging ...but main battery is fine ...i left both negative cables off for 30 minutes came back and hooked everything up and it was reading 14.5 volts and didnt drop when driving ...then this morning started at 13.9 when running and down to 13.7 after a few minutes ...seems as the thou the alternator doesnt charge when its supposed to ...so maybe something in the PCM controls or voltage regulator that i presume in the alternator itself ... and BTW is the service manager at the dealership that told me the alternator charges part time .....just an FYi ....called the dealer but the whole dealership is closed today due to a Power outage ,,,,so i guess im not alone
 

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all connections good ...belt is good ....i have a battery alternator tester i bought a few years ago and shows as of yesterday the aux battery is dead,, and alternator wasnt charging ...but main battery is fine ...i left both negative cables off for 30 minutes came back and hooked everything up and it was reading 14.5 volts and didnt drop when driving ...then this morning started at 13.9 when running and down to 13.7 after a few minutes ...seems as the thou the alternator doesnt charge when its supposed to ...so maybe something in the PCM controls or voltage regulator that i presume in the alternator itself ... and BTW is the service manager at the dealership that told me the alternator charges part time .....just an FYi ....called the dealer but the whole dealership is closed today due to a Power outage ,,,,so i guess im not alone
and all if this is in the last two weeks ....it never did this before
 

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all connections good ...belt is good ....i have a battery alternator tester i bought a few years ago and shows as of yesterday the aux battery is dead,, and alternator wasnt charging ...but main battery is fine ...i left both negative cables off for 30 minutes came back and hooked everything up and it was reading 14.5 volts and didnt drop when driving ...then this morning started at 13.9 when running and down to 13.7 after a few minutes ...seems as the thou the alternator doesnt charge when its supposed to ...so maybe something in the PCM controls or voltage regulator that i presume in the alternator itself ... and BTW is the service manager at the dealership that told me the alternator charges part time .....just an FYi ....called the dealer but the whole dealership is closed today due to a Power outage ,,,,so i guess im not alone
Now you've got an aux. battery and AGM's.
As i said, AGM batteries are a different animal compared to the old lead acid batteries.
With AGM's there's an important no load voltage measurement called State of Charge (SOC).
A properly no load 100% charged AGM battery's SOC is approx. 12.7 to 13 VDC depending on when it was last charged, battery mfg, ambient temperature, etc.
13.7 Volts should be enough to trickle charge the battery when the PCM decides it doesn't need any more hi amp charging.
If your Jeep cranks reliably in the morning and thereafter i don't think there's any thing to worry about.
 
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Most newer vehicles have a smart charging system that varies the charge current to reduce engine load/emissions. Often there is no charging during periods of low RPM. You will see varying voltages on the battery but this does not necessarily mean the alternator is faulty. Yes, it is all about State-of-Charge (SOC).

Check this for further info: Smart Charging
 

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well its on its way back to the dealer today to get checked ...if it did this from the day i bought it ...id buy the explaination ...however ive had the jeep over 2 years now and it never did this til two weeks ago ...soooooo ...something is obviously amiss,....apparently it COULD be something called a Battery voltage controller ..???? if u see a Battery voltage meter keep jumping from low to high and to low to high exct ,...like 5 times in a few minutes ,,,,something is WRONG :)
 

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well its on its way back to the dealer today to get checked ...if it did this from the day i bought it ...id buy the explaination ...however ive had the jeep over 2 years now and it never did this til two weeks ago ...soooooo ...something is obviously amiss,....apparently it COULD be something called a Battery voltage controller ..???? if u see a Battery voltage meter keep jumping from low to high and to low to high exct ,...like 5 times in a few minutes ,,,,something is WRONG :)
Keep us updated on what the dealer finds.
 
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