Fluctuating Voltage Issues

[Dr. RGB]

Good Morning Jeepers! So, I have been experiencing something that I find interesting and have never witnessed before. Now, I will say that I do not monitor my Voltmeter in the Jeep on a regular basis, but here are some of the things I have been seeing over the past few weeks. For reference, this is a 3.6 6M, no codes or warnings at all, and there have been no ill effects to any of the electronics in the Jeep.


1. Normally, my Jeep voltmeter usually reads between 14.2 and 14.4 volts.
2. Over the past few weeks, peak volt has been dropping from 14.2 to 13.8 to 13.6 and coming home from a Jeep event last night, dropped and stayed at 12.7.
3. Increasing engine RPM's does nothing to the volt level. The Jeep stays at 12.7 volts.
4. When in gear and allowing for engine braking, the volt level will shoot back up to 13.7 volts.
5. Push in the clutch, drops back to 12.7.

In summation, at idle and under load, the voltmeter is reading 12.7 (and continues to drop day to day). Only during engine braking, do the volts increase (13.7 volts). I am going to replace both batteries today and see if this makes a difference. I hope it is not the alternator!

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[Rhinebeck01]

@Dr. RGB

Would be interesting to talk to you and ask a few questions but what you are seeing is pretty typical...

Your #1 was probably the result of your typical, not driving the JL that much routine.... and then when you did drive the JL, the alternator would be working hard... and you'd see 14.1 - 14.2 .

As for the 2, 3, 4, 5 pretty typical to see when you are on/during a long road trip for example. Or on a vehicle that gets lots of driving time.

Once the batteries(2) get charged up, the alternator can take breaks so to speak.... when on breaks... working easily, you will see 12.8, 13, etc..

Also, to see fluctuations of alternator reading with braking, cruising, up hills and such is normal.

Your 2020 JL may very well need 2 new batteries but what you are saying here, to me, is not a sign of issues with alternator or batteries.

 

[Dr. RGB]

@Dr. RGB

Would be interesting to talk to you and ask a few questions but what you are seeing is pretty typical...

Your #1 was probably the result of your typical, not driving the JL that much routine.... and then when you did drive the JL, the alternator would be working hard... and you'd see 14.1 - 14.2 .

As for the 2, 3, 4, 5 pretty typical to see when you are on/during a long road trip for example. Or on a vehicle that gets lots of driving time.

Once the batteries(2) get charged up, the alternator can take breaks so to speak.... when on breaks... working easily, you will see 12.8, 13, etc..

Also, to see fluctuations of alternator reading with braking, cruising, up hills and such is normal.

Your 2020 JL may very well need 2 new batteries but what you are saying here, to me, is not a sign of issues with alternator or batteries.

Excellent! I am going to run to AutoZone and get some new batteries and we will see what happens. BTW, could FCA designed the AUX battery location in a more challenging location?!?!?!

 

[Rhinebeck01]

Excellent! I am going to run to AutoZone and get some new batteries and we will see what happens. BTW, could FCA designed the AUX battery location in a more challenging location?!?!?!

YIKES............. For anyone seeing this pic.... Do not dismantle your PDC to get to the Aux battery that resides under it. You could easily do a thousand $ plus damage doing the Aux change out this way..

Read here:
https://www.jlwranglerforums.com/fo...ent-the-easy-way-pull-the-fender-flare.56807/

 

[Dr. RGB]

YIKES............. For anyone seeing this pic.... Do not dismantle your PDC to get to the Aux battery that resides under it. You could easily do a thousand $ plus damage doing the Aux change out this way..

Read here:
https://www.jlwranglerforums.com/fo...ent-the-easy-way-pull-the-fender-flare.56807/

Well, we are in it to win it now. Fingers crossed.

 

[Rhinebeck01]

If you do want to replace both batteries:

A JL or JT with tow package leaves the factory with an H7-AGM Group Size 94R Main battery.

A JL or JT without the tow package leaves the factory with a Group 48 H6 Main battery, which is a tad shorter in length then the H7-AGM Group Size 94R.

With that said, if you go to install an H7-AGM Group Size 94R battery in a JL or JT that left the factory with a Group 48 H6 battery you will, in order to install the H7, have to remove a small plastic stay you will find fastened into the bottom of the Main's battery holder box. The stay comes out very easily.

For those replacing your JL or JT's Main battery... you are best served going with a higher CCA H7 versus installing a lesser CCA H6. Should also mention that often you will find the H7 costs the same as an H6.

Note: When buying an H7 is is prudent to first remove your current Main battery and measure the length of the box with the plastic stay removed. Compare that length measurement to the physical length of the H7 battery you are thinking about buying..

For your JL/JT , here are some H7's that are known to fit the JL/JT Main battery box with the stay removed:

Interstate MTX-94R/H7 850CCA 80 Ah AGM
Odyssey Performance AGM94R H7 L4 840 CCA
Super Start Platinum H7 SSB94RPLT 800 CCA
Napa P/N 9894R H7 800 CCA
Batteries+ X2 Power H7 Group 94R SLI94RAGMDP 840 CCA
EverStart Platinum AGM Battery, Group Size 94 H7 850 CCA (Walmart)
Optima YELLOWTOP AGM YEL94R DH7 Group 94 880 CCA
DieHard Platinum AGM Lead Acid Battery, Group H7, 850 CCA


For Aux battery:
Aux battery replacement:

DieHard Platinum AGM Battery, BCI Group Size 400, 200 CCA
Part # AUX14-1

Super Start Platinum Auxiliary Battery Group Size 400
Part #AUX14

Braille (Part# B14115) I5Ah 360CCA
Tests from factory at 483 Crank Amps. Wt. 11.5 lbs.

For Aux battery change the easy way and more battery related info read here:
https://www.jlwranglerforums.com/fo...ent-the-easy-way-pull-the-fender-flare.56807/

 

[Rhinebeck01]

Looking at your pic and ... oh my ..... ...... anyway, good chance you have already or will be blowing a fuse in your high amp fuse array. Forum search with the words N3, blown, high amp fuse array.

If if the N3 blows, your alternator will no longer charge the Aux battery and you will see other issues...

So, FYI..... there are two different high amp fuse arrays.
Difference is one has a 60 amp fan fuse and the other has a 100 amp fan fuse. That is the only difference but yes, they are different and you need to keep this in mind.

By the way.... having the tow package is what dictates that you use the fuse array with the 100 amp fan fuse.

68368853AA Mopar Z Case Fuse Array (has the 60 amp fan fuse) and 68368854AA
Mopar Z Case Fuse Array.... (has the 100 amp fan fuse)

 

[Jim1964]

So, you’re replacing the batteries even with it operating normally and no mention of problems with cranking?

 

[swampflyer]

Anyone close to me that needs replacement batteries I have the two out of my JLR for free, the main and the aux, when I converted to the Genesis dual system. You pu the the batteries. They were in perfect shape when replaced.

 

[Rhinebeck01]

So, you’re replacing the batteries even with it operating normally and no mention of problems with cranking?

@Jim1964

I think the OP, may have misinterpreted what he was seeing going on battery(2) / alternator wise and then went on a mission so to speak.

Wish he had come here first and researched... especially before he dismantled the PDC on his JL.

Regardless ..... I do think that changing out the 2 batteries on his 2020 JL is a good move on his part.. The 2 batteries are undoubtedly both on their last legs... aged/aging out...

Good idea to change them out now..... versus having battery(2) issues and say being stuck with a no start situation on a cold, snowy day in PA .... (OP resides in Pa)

 

[Dr. RGB]

Replaced both batteries and the Jeep is not on fire (my Jeep is MY 2020, but built in 2019, so the batteries were probably going to go and I would rather not be stuck). Everything is working as normal. Battery voltmeter in the Jeep shot back up to 14.2. I have not seen that in about two months. I'll report back if there are any issues.

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