Alternator max volts

rmartin · **Joined:** Sun Sep 23, 2012 4:23 pm **Posts:** 12

06 Liberty CRD, replaced alternator in Feb, left key on night before last, 6 year old optima dead as a door nail, jump started it and drove 2 hours. During the drive noticed my plug in volt meter was up to 15.3 volts. Parked and over night the volts dropped from 13.2 when I shut it off down to 11.9 the next morning. Jeep started just fine at 11.9, charged it up to 13.2 again and over night dropped to 11.9 again. Nothing left on during those 2 nights, but battery drops over night to 11.9.
Figure I need a new battery, but is the new alternator over charging the battery at 15.3?
What is correct max alternator out put voltage?
Do not want to buy new battery if alternator that is still under extended warranty is going to ruin another battery.
Thanks Richard

Goglio704 · **Posted:** Sun Sep 23, 2012 5:41 pm

I can't quote a spec, but that sounds like what mine does. I think you are safe with replacing the battery.

tjkj2002 · **Posted:** Sun Sep 23, 2012 7:50 pm

A good alternator,and voltage regulator as yours is in the ECM,will put out between 13.2 volts and 14.8 volts.Any more or any less and you got a bad alternator or bad ECM.A bad battery can skew those #'s a little but not over 15 volts or under 13 volts if the charging system is good.

Billwill · **Posted:** Mon Sep 24, 2012 3:01 am

tjkj2002 wrote:

A good alternator,and voltage regulator as yours is in the ECM,will put out between 13.2 volts and 14.8 volts.Any more or any less and you got a bad alternator or bad ECM.A bad battery can skew those #'s a little but not over 15 volts or under 13 volts if the charging system is good.

@tjkj2002 What year did Jeep change from having the ECU do the regulation to have a different alternator with the regulator built in?

I thought that it was from the 2006 model KJ that the alternator had a built in regulator and only received a "wake up" call from the ECU at 2,000 RPM to tell the regulator to start regulating. I know Keith from GDE posted on this topic but I cannot find it at present.

Either way the actual sensing of the voltage I gather is done some distance from the battery itself, namely at the ignition switch, so any bad connections or bad grounds could fool the regulator into thinking that the voltage is too low and needs to be increased.

msilbernagel · **Posted:** Mon Sep 24, 2012 3:23 am

With the key off and a fully charged battery you should see 12.6V...

Mark

Hoosier CRD · **Posted:** Mon Sep 24, 2012 5:51 am

Charging the dead battery by driving it causes the alternator to work overtime, like you have seen. An alternator maintains the charge of the battery. The best scenario is to re-charge the battery with a charger. You may not have been able to do that for various reasons. I typically see 13.6 to 14.8 volts as being the good range. I guess 13.2 is acceptable.

Yes, it sounds like your battery is toast. It is not holding the charge needed to function properly. 12.6-12.8 volts is usually what one will see on a new, fully-charged battery. Or on an in-use/properly functioning battery. When a new battery is installed all of the other components in the starting and charging system will show their true function, good or bad. Hopefully all you have is a dead Optima and once replaced all is back to normal.

Joe Romas · **Posted:** Mon Sep 24, 2012 9:05 am

I think it's been brought before that the CRD's alternator has a conventional built in regulator unlike the gas models.

Additionally the full charge voltage of a red top is12.6 volts that's lower then normal.
It does sound as if the op's red top is bad or worse then normal :dizzy:

You can't beat a expensive Sears P1 :JEEPIN:

Billwill · **Posted:** Mon Sep 24, 2012 11:09 am

Joe Romas wrote:

I think it's been brought before that the CRD's alternator has a conventional built in regulator unlike the gas models.

Additionally the full charge voltage of a red top is12.6 volts that's lower then normal.
It does sound as if the op's red top is bad or worse then normal :dizzy:

You can't beat a expensive Sears P1 :JEEPIN:

Joe, if I look at the circuit diagrams for the 2003 and the 2006 KJs....they both show that Gas and Diesel alike....the regulation is done by the ECU or PCM ie. there is no built in regulation in the alternator...only a diode pack.

I do not have the circuit diagram for the 2007 KJ...maybe that is the only KJ that has built-in regulation in the alternator.

Either way, I agree with you that a good new battery will probably resolve the problem.

Joe Romas · **Posted:** Mon Sep 24, 2012 2:21 pm

Billwill wrote:

Joe Romas wrote:

I think it's been brought before that the CRD's alternator has a conventional built in regulator unlike the gas models.

Additionally the full charge voltage of a red top is12.6 volts that's lower then normal.
It does sound as if the op's red top is bad or worse then normal :dizzy:

You can't beat a expensive Sears P1 :JEEPIN:

Joe, if I look at the circuit diagrams for the 2003 and the 2006 KJs....they both show that Gas and Diesel alike....the regulation is done by the ECU or PCM ie. there is no built in regulation in the alternator...only a diode pack.

I do not have the circuit diagram for the 2007 KJ...maybe that is the only KJ that has built-in regulation in the alternator.

Either way, I agree with you that a good new battery will probably resolve the problem.

Here is where MrMopar says otherwise :jester:

viewtopic.php?f=5&t=53992&p=602687&hilit=alternator+pulley#p602687

tjkj2002 · **Posted:** Mon Sep 24, 2012 8:32 pm

Joe Romas wrote:

Billwill wrote:

Joe Romas wrote:

I think it's been brought before that the CRD's alternator has a conventional built in regulator unlike the gas models.

Additionally the full charge voltage of a red top is12.6 volts that's lower then normal.
It does sound as if the op's red top is bad or worse then normal :dizzy:

You can't beat a expensive Sears P1 :JEEPIN:

Joe, if I look at the circuit diagrams for the 2003 and the 2006 KJs....they both show that Gas and Diesel alike....the regulation is done by the ECU or PCM ie. there is no built in regulation in the alternator...only a diode pack.

I do not have the circuit diagram for the 2007 KJ...maybe that is the only KJ that has built-in regulation in the alternator.

Either way, I agree with you that a good new battery will probably resolve the problem.

Here is where MrMopar says otherwise :jester:

viewtopic.php?f=5&t=53992&p=602687&hilit=alternator+pulley#p602687

The alternators voltage is not controlled inside the alternator for any US CRD,call that circuit what ever you want but it's not inside the alternator.

rmartin · **Joined:** Sun Sep 23, 2012 4:23 pm **Posts:** 12

Thanks to all for the help, Liberty is holding 11.9 to 12.3 in the mornings, down from 13.2 after a hour drive. Going for the Die Hard Platinum . Thanks Richard

ATXKJ · **Posted:** Mon Sep 24, 2012 8:55 pm

my Alternator voltage was flaky (oscillating up between 11 and 15)

- dealership replaced the alternator (under warranty)

- fixed it.......

spitfire36o · **Posted:** Tue Sep 25, 2012 9:49 am

After I installed my renegade roof bar, I noticed my lights occasionally dim when im off the gas. This didnt happen all the time. Then iIstarted to notice pulsing when the rpm's are up. I opened up my torque app the last time they were acting up. During the pulsing, my voltage was peaking at 15.2v. When i would let off the gas and they would dim, the volts would drop to 11.5v. I'm on the original red top from 05, so i may just replace that and see if it fixes it. Otherwise, the next step would be checking all my ground points. And finally, replacing the alternator.

geordi · **Posted:** Tue Sep 25, 2012 10:47 am

Start by replacing the alternator's pulley, and forget about any of that other stuff. The pulsing is because the clutch in the pulley has worn out. Many people just replace the entire alternator, which is also a good fix for this problem. Autozone has lifetime warranties on the alternator, and sells the whole unit with the proper pulley for $150.

spitfire36o · **Posted:** Tue Sep 25, 2012 2:00 pm

geordi wrote:

The pulsing is because the clutch in the pulley has worn out.

No, it is not. The decoupler pulley was changed 10k miles ago. The serpentine belt and tensioner were changed 5k miles ago. You cant just state that "this is because of that" without knowing the service history. I appreciate all the help and advice from this forum, but you cant just make a blind diagnosis like that. A voltage spike above 15v would not be explained by a slipping belt either; only voltage drops.

tjkj2002 · **Posted:** Tue Sep 25, 2012 2:11 pm

spitfire36o wrote:

geordi wrote:

The pulsing is because the clutch in the pulley has worn out.

No, it is not. The decoupler pulley was changed 10k miles ago. The serpentine belt and tensioner were changed 5k miles ago. You cant just state that "this is because of that" without knowing the service history. I appreciate all the help and advice from this forum, but you cant just make a blind diagnosis like that. A voltage spike above 15v would not be explained by a slipping belt either; only voltage drops.

Just because the pulley was replaced 10k ago does not mean it's any good right now.

spitfire36o · **Posted:** Tue Sep 25, 2012 2:36 pm

tjkj2002 wrote:

Just because the pulley was replaced 10k ago does not mean it's any good right now.

I understand a bad pulley or lose belt explaining voltage drops, but how would a bad pulley explain a voltage spike?

tjkj2002 · **Posted:** Tue Sep 25, 2012 3:14 pm

spitfire36o wrote:

tjkj2002 wrote:

Just because the pulley was replaced 10k ago does not mean it's any good right now.

I understand a bad pulley or lose belt explaining voltage drops, but how would a bad pulley explain a voltage spike?

Your alternator pulley is basically a one-way bearing,if not functioning correctly your alternator may not work right.

spitfire36o · **Posted:** Tue Sep 25, 2012 4:29 pm

tjkj2002 wrote:

Your alternator pulley is basically a one-way bearing,if not functioning correctly your alternator may not work right.

Gotcha, now i understand...

Joe Romas · **Posted:** Thu Sep 27, 2012 10:52 am

TJ and others.

It sure looks like the 05/06 CRD Liberties have built in regulators like MrMopar64 says
Here's some sites that list specifications and that say INTERNAL REGULATORS
Looking at wiring diagrams in the FSM it indicates there's a temperature sensor located in the battery box/tray but there is not.
Go look for your selves, you'll find there is no temperature sensor in the CRD's battery box.
The three sites below say INTERNAL regulator.
Most sites don't specify either way.
The tag on my newly dealer replaced alternator says it's a Denso 104210-4242 and doing a search on that is a dead end :dizzy:

The Jeep/Chrysler part number on the tag is 56044672AB

http://universal-alternators.co.uk/Product/DRA0168.aspx
http://shop.advanceautoparts.com/buy/pr ... fragment-2
http://www.amazon.com/REPLACEMENT-ALTER ... B008FTODU6

Alternator max volts

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