The Dreaded Alternator Pulley

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

Yea I used an impact. I see the kit now lol. Thx!

WWDiesel · **Posted:** Fri Jul 17, 2020 9:24 pm

jagster936 wrote:

My dad showed me this now I feel really stupid. I got her swapped when used the Allen I was thinking that was a center bolt like many other pulleys Ive dealt with! Thank you!
In method you describe you need a way to hold the center shaft. Some sort of special tool? Or a 17mm Allen that is hollow so you can hold shaft?

The 17mm hex tool in the kit is hollow inside and comes with a 10mm tool that holds the shaft through the hollow shaft of the hex... :wink:

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

That would be nice LOL

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

Ok this crazy thing. I replaced pulley a while back and light fluctuations went away. This was maybe 1-2k max miles ago. Now it started fluctuating again! Usually when you let off throttle and it falls to around 1200rpm flickers pretty bad. Did that darn pulley fail again or do I need regulator / alternator?

WWDiesel · **Posted:** Sun Dec 13, 2020 4:36 pm

jagster936 wrote:

Ok this crazy thing. I replaced pulley a while back and light fluctuations went away. This was maybe 1-2k max miles ago. Now it started fluctuating again! Usually when you let off throttle and it falls to around 1200rpm flickers pretty bad. Did that darn pulley fail again or do I need regulator / alternator?

Put a volt meter on the alternator output terminal, it will tell all. :wink:

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

I’ll have to trend it. The lights tell all also it acts just like the pulley did and I was told
It was the pulley. And it seemed to be.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

The pulley is just a one-way clutch that prevents wear on the serpentine belt (and maybe a saves a little fuel) by "disengaging" it when the engine speed is dropping... the alternator slows down "naturally" even as your foot is off the gas. WW's test is the test - make sure voltage from the alternator is stable. If it' not, either the pulley has failed and it's no longer engaged on acceleration, or the alternator is failing and can no longer produce sufficient voltage at low speed, or you have a problem with the battery or its cables resulting in excessive voltage drop/high resistance/bad conductivity. It's worth noting that pulleys don't typically fail to "no drive" they typically fail to "no clutch." Put another way, you generally won't run into a problem where you don't get charging due to a failed pulley, you typically get noise or other artifacts because the pulley won't (fully) disengage on overrun.

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

It isn’t battery connections. Makes no sense as it behaves in a certain way and actively fluctuates as I stated. It’s pulley or regulator. Seems odd regulator would be so predictably speed related. Yet also odd since pulley is brand new and others swore it was the issue. And it was for a while ... lol.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

What you describe definitely does not sound like a bad pulley or have anything to do with the pulley. Fluctuating voltage at low RPM is typically either an alternator that cannot supply sufficient amperage at a reduced speed or a battery that lacks sufficient capacity to flatten out the crazy voltage transients all alternators create. Or, like I said, a cable/connection issue between the alternator/battery/chassis that results in severe voltage drop... Don't forget that what we see as perceptible flicker could represent less than 1v of actual variance.... it takes only a slightly iffy connection to produce that sort of loss.

Have you had the alternator tested? Monitored ECM voltage with an OBDII tool? Checked for bad grounds or high resistance on cables? Load tested the battery?

The alternator pulley has two functions - engage on drive and disengage on overrun. I don't see how a pulley could be involved in flickering lights. If it's partially locking on overrun (which is a weird failure mode) and the alternator is running at an inconsistent speed, it should be able to provide a full 14v. It's be hell on the alternator and/or belt, but it shouldn't impact output. If it's slipping on drive, the battery should be able to fill in the gaps.

I think you'd see that very quickly with a voltmeter on the battery terminals I'd think. Just spitballing, but I'm thinking maybe the reason is seemed fixed for a while was an external circumstance.... like a damaged cable being moved just so when you replaced the pulley but eventually settled into its old position, a connection getting cleaned up, or even just the weather. Batteries suck in cold weather.

My XR4Ti had a similar issue that haunted me for a year - every time I replaced the alternator it was fine for a few months, and then the lights would get dimmer. After two alternator replacements I started taking things apart and found the alternator B+ cable was basically in two pieces inside the insulation. When I removed & reinstalled it, the pieces would get closer together, but after a while it would settle into its old position and the damaged conductors would open up. Replaced the last 3' of that cable (to get back into the harness) and no more problems in 10+ years.

Does the CRD have ECM controlled charging like GM cars do? That could be another angle.

WWDiesel · **Posted:** Tue Dec 15, 2020 10:13 pm

I fully agree with thesameguy,
Put a volt meter on the output terminal of the alternator and watch the voltage output at the affected RPMs.
Then put the volt meter on the battery and measure the voltage input to the battery at the affected RPMs.

I find it extremely hard to believe that an alternator override pulley could cause a true voltage oscillation problem. Something else is going on!
The pulley either works or it don't. Normally if the pulley fails, they simply completely freeze up (lock up) and quit performing the overrun function completely during deacceleration and during the pulses at idle.
Normally when you see alternator output voltage oscillation, it is a voltage regulator issue or the device controlling the voltage regulator. :wink:

If nothing is wrong with your cables or connections, I would replace the alternator.

flash7210 · **Posted:** Tue Dec 15, 2020 10:14 pm

jagster936 wrote:

It isn’t battery connections. Makes no sense as it behaves in a certain way and actively fluctuates as I stated. It’s pulley or regulator. Seems odd regulator would be so predictably speed related. Yet also odd since pulley is brand new and others swore it was the issue. And it was for a while ... lol.

I’ve experienced this problem.
It’s definitely the voltage regulator.
I found a replacement regulator on eBay, repaired the alternator, and all was better.

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

Wow thanks for all the great info. I’ll have to look into this a little deeper!! I will post results when I find time to troubleshoot.

Billybob · **Posted:** Wed Dec 16, 2020 2:58 am

@jagster936 what year is your CRD? :wink:

The 2005 CRD the alternator voltage regulation is done via the FCM (Front Control Module) which is a small module in the center of the engine bay.
This module gives a lot of problems...it is subject to having its connector get gunged up with water, snow, mud etc. The Brown/Dark Green wire goes from the Alternator to the FC via connector# C114 pin 1. The connector locations are shown at the end of the Wiring Diagram index.

So first clean the FCM and check connector # C114.

The 2006 CRD gets its regulation from the BCM which is on the rear of the internal fuse panel...via connectors C114 and C120.

I presume you have the Service Manuals for your year CRD?

Plug your Multimeter into the front power outlet so you can monitor the voltage as you drive!

flash7210 · **Posted:** Wed Dec 16, 2020 5:06 am

Billybob wrote:

@jagster936 what year is your CRD? :wink:

The 2005 CRD the alternator voltage regulation is done via the FCM (Front Control Module) which is a small module in the center of the engine bay.
This module gives a lot of problems...it is subject to having its connector get gunged up with water, snow, mud etc. The Brown/Dark Green wire goes from the Alternator to the FC via connector# C114 pin 1. The connector locations are shown at the end of the Wiring Diagram index.

So first clean the FCM and check connector # C114.

The 2006 CRD gets its regulation from the BCM which is on the rear of the internal fuse panel...via connectors C114 and C120.

I presume you have the Service Manuals for your year CRD?

Plug your Multimeter into the front power outlet so you can monitor the voltage as you drive!

I can say with 100% confidence that this is incorrect.
Both 05 and 06 model alternators are exactly the same.
The voltage regulator is built into the alternator and is the only thing controlling the charging voltage to the battery. FCM and BCM have nothing to do with it.
I’ve tested and confirmed this.

Billybob · **Posted:** Wed Dec 16, 2020 8:44 am

OK let me re-phrase my statement.

The alternators have built-in regulators but they are "kicked" into action by the BCM.

At engine turn-over the alternators are not energized so as to reduce strain on the starter motor....after a second or two the alternators are kicked into life.
Possibly in this case the alternator is not being kicked into life and problems start as the battery gets drained.

Keith from GDE had very good information on how this worked and how it differed to the 3.7 gassers and did post this info here on the Forum somewhere. The 2.4L gasser also used a one-way pulley similar to the CRD but I have no idea as to how their voltage regulation works.

I believe that it is unlikely that once the alternators are operating they should not be affected by the BCM or FCM so why the voltage seems to drop while running with lights ON must be bad grounding or wiring issues somewhere.

So I would monitor the battery voltage while running to try see if there is any pattern as why the voltage is dropping....move harnesses around, switch lights ON etc. :wink:

Or replacement alternators or pulleys are faulty! :shock:

The original pulleys were dry but I believe the newer Mopar CRD pulleys are oil-filled and more reliable. :wink:

jagster936 · **Joined:** Sun Aug 04, 2019 3:06 pm **Posts:** 210

Interesting. I think you’re right about a control module kicking it on. Whether it causes issue I’m not sure. I think I have a 2005 will have to double check. Thx for the info. Seems it’s likely the alternator regulator. I may try fixing or just replace whole thing like I do any other car. But the oem alternators are beefy so maybe replacing the regulator only is better. I did similar for my Tacoma just did stater motor brushes. The windings are very robust and tend to last forever.

CATCRD · **Posted:** Wed Dec 16, 2020 1:00 pm

From the 2005 SM:

Quote:

VOLTAGE REGULATOR
DESCRIPTION
The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulating
circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
OPERATION
The amount of DC current produced by the generator
is controlled by EVR circuitry contained within
the Powertrain Control Module (PCM). This circuitry
is connected in series with the generators second
rotor field terminal and its ground.
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage (B+) and
battery temperature (refer to Battery Temperature
Sensor for more information). It then determines a
target charging voltage. If sensed battery voltage is
0.5 volts or lower than the target voltage, the PCM
grounds the field winding until sensed battery voltage
is 0.5 volts above target voltage. A circuit in the
PCM cycles the ground side of the generator field up
to 100 times per second (100Hz), but has the capability
to ground the field control wire 100% of the time
(full field) to achieve the target voltage. If the charging
rate cannot be monitored (limp-in), a duty cycle
of 25% is used by the PCM in order to have some
generator output. Also refer to Charging Operation
for additional information.

In the 2005 this is indeed controlled by the FCM. That is the only thing connected to the plug on the alternator. In the 2006 it is done by the BCM.

Question to flash7210: Do you have a link to what you replaced in your alternator? Was it a rectifier?

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

I don't know what I am talking about, but my belief is the alternator still must have a traditional voltage regulator, but rather than getting charging info directly from the B+ terminal it's routed through a control unit for finer tuning (so as to not waste hp with unnecessary output). This is similar to GM cars of the era, and what I'd asked about in the post above. If the connection to and from the control module to the alternator is iffy, you can get some voltage fluctuations as a result... As CATCRD indicated. It would definitely be worth inspecting the FCM/BCM for any correlation at the connector, and the wiring for any damage. It's probably a pretty fine wire - 16g or maybe less - And subject to trauma.

WWDiesel · **Posted:** Wed Dec 16, 2020 3:07 pm

The voltage regulator is replaceable on both the 05 & 06 models.
On the 05, the single wire does go directly to the FCM where it communicates the signal to either the ECM or the BCM over the Can Bus/Data Link.
On the 06, the single wire goes directly to the BCM where it communicates to the ECM over the Can Bus/Data Link.
The big question is: Is the single wire controlling the voltage regulator excitation of the alternator to control voltage output or is it simply monitoring the status of the alternator output?
The FSM says: "GEN FIELD CONTROL", "Control" clearly being a key word.
Not 100% sure exactly how the voltage regulator controls the alternator output in relation to the field control wire coming from the Front Control Module Gateway if it does indeed control or just monitor. The FSM certainly is not clear in how control is performed.
As I have stated many times, what we really need for these vehicles is Control Logic Block Diagram, that would tell us SO much helpful information when trying to diagnose electrical problems... :banghead:

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Yeah, documentation would be VERY helpful. One thing that's always weird when working on older cars is that often times the documentation assumes certain tools or diagnostic procedures aren't available... I run into this a lot with older European cars where you need a magic factory tool, or resort to parts swapping. In 1985, that was the option. In 2020, you jump on Amazon and buy a $50 software oscilloscope and get the actual answer.

It could be that in 2005 the Jeep diagram wasn't deemed useful because nobody would have the tools for follow it.

Anyway, I think most of these computer controlled charging systems work in a similar manner - the control module correlates conditions (things like load, ambient temp, battery state of charge, etc.) and then uses pulse width modulation (PWM) to cause the regulator to switch the rotor’s field coils.... A higher duty cycle is more charging, and a lower duty cycle is less charging. GM does this with three wires IIRC (charging, sensing, control) but it could be done with two wires (charging+sensing, control). The difference would solely be where the control module gets current charge info... depending on how the car is wired, that variance could be big or small - but obviously in a car *designed* to have two wires, that would be accounted for. I think a lot of modern cars have a central or main battery distribution point for this purpose, so the control module can accurately measure alternator output and exert this control.

Here's an article on the topic specific to Chrysler:

https://autoprollc.com/wp-content/uploa ... ly_web.pdf

One thing that occurs to me, and probably worth keeping in mind, is that it seems the Liberty CRD doesn't behave like typical Mopars in most ways, so it wouldn't surprise me *at all* to find the Jeep's charging system is not Chrysler-like. But, there are some commonalities in the image WW posted and this article.

In that article, this bit:

Setpoint Regulation
To maintain the desired voltage setpoint, the regulator (PCM) controls either the power or ground circuit of
the rotor to maintain the proper magnetic field strength. The required current flow of the rotor varies based
on vehicle demand, battery state of charge and engine RPM. Chrysler applications have used both A and B
side regulation.

refers to the control module PWM control of the regulator.

The Dreaded Alternator Pulley

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