I am currently experiencing a intermittent alternator! I was driving to work and noticed my lights seemed like they were dimming and the interior fan was fluctuating in speed. Then the dash lights went haywire and the speedometer was jumping around and the engine was kind of chugging along. After a few km's everything levelled out and I got to work. At work i went out with my multimeter and the voltage was reading fine around 14.2~. A check engine light stayed on while driving home but nothing strange happened

I thought it was just a hiccup and tried to use my innova 3120 to read the code but It doesn’t seam to work with the CRD so I cant give any codes.

After driving around tow the MIL went out on its own. But then later the same problem happened all over again.

I tried a known good battery I have and connect my multimeter to the cigarette light and drove around town again. I noticed the voltage would drive below 12v but then from time to time climb back up to 14.2~. Very strange problem! not sure what to try next. It seems to me like the alternator is fine and it’s the Gen Field Signal from the Computer. I got a service Manuel here and it said that the signal should cycle up to 100hz and vary in frequency to vary the current. I measure the freq with my meter and read a sporadic freq jumping as high as 350hz. But that could be just loose connections to my meter. Another though its could it be the ASD relay? Apparently this relay activates the voltage sense circuit in the PCM. Not sure where to find that one!

Or am I just over analysing all of this and it’s just the alternator is bad. The problem is I only have 71k KM's or 44k Miles. It seams unlikely that my alternator could already be gone.

Any help would be greatly appreciated

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2006 Jeep Liberty CRD /w GDE ECO Tune

1998 VW Jetta TDI

1995 Pontiac Sunrunner (Soon to have a diesel)

Do you think it could just be the alternator clutch pulley? Those are known to have a finite lifetime. You may be the first person sophisticated enough to measure the frequency of the output.

I think there was a few here that had trouble with the BCM and the cure was to replace it.

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2006 Black Jeep Liberty CRD Limited
K&N, Samco Hoses, Michelin 245/70-16 LTX A/T2, Fumoto F-102, V-Force Muffler, Mopar, Hitch, Trailer Wiring, Skid Plates, Slush Mats, Rear Shelf, Predator Stage 1, Transgo, ORM & CodeReader, Facet 40109 Pump
"IT'S A DIESEL THING, YOU WOULDN'T UNDERSTAND"
Certified Services Auto & Truck Repair

Check your coupler on the alternator first.
What year model is your CRD?
There has been a lot of discussion on this forum I think about what exactly controls the field coil on the alternator.
I know on the earlier CRDs the field coil is definitely controlled by the ECM....the ground is cycled as you say with a varying frequency. There is also a voltage sense wire going to the ECM whereby it senses if it need to up the output to the field coils.
If your alternator coupler is good, I would suggest you disconnect the battery and re-plug the connectors on your ECM and also check your battery ground connectors.
I have had problems in this area with my 2002 2.5 CRD which ended up being several bad wires in one harness...fortunately I have the circuit diagram for the 2002 model so I could trace the faults.

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2002 Export CRD 2.5 Sport

It may be that your tensioner is going bad on the serpentine belt too. The alternator skips and slides until the belt tightens at-speed and the alternator is able to work. Turn the A/C on (or put it on defrost) and brights on before you start the machine and see if anything squirrelly starts happening when you start it (the A/C and alternator BOTH pulling on a cold serpentine belt should make a noise...).

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2005 CRD Sport - "Blackie"
Tow Package
Trac Loc
GDE EcoTune w/ unl torque
Goodyear Wrangler SilentArmor Tires
over 192,000+ miles
100k mile service performed
5V Glow Plugs Installed and ECM updated

Thanks a lot guys! Those are some great tips! I will let you know what I find. Never thought of the belt tensioner! That might be it since the AC is usually on when I get the problem.

Now one question, if the pulley on the alternator was bad could it be a silent problem or do they usually squeal and make a lot of noise. What it weird is I have no noises out of the ordinary!

Thanks,

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2006 Jeep Liberty CRD /w GDE ECO Tune

1998 VW Jetta TDI

1995 Pontiac Sunrunner (Soon to have a diesel)

If the decoupler pulley on the alternator is bad it does not make any noise it just does not let the alternator put out any charge to the battery. I replaced mine in 08 for about $55 and have not had any problems since. The alternator should have a output around 14.2 amps. I doubt it is the tension er you would see it bouncing around if it was bad.

I got the alternator out today! The tentioner was fine and I loaded down the belt system by turning on the ac and blasting the fan! And the belt seamed to run just fine.

With the alternator out I inspected the pulley and it looked like it has already been replaced. There was also a sticker on it from K and P Auto Marine Electrics. A shop in Mississauga that rebuilds these I guess. So maybe something went bad since the rebuild, not sure but I will take it in for testing and let you all know.

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2006 Jeep Liberty CRD /w GDE ECO Tune

1998 VW Jetta TDI

1995 Pontiac Sunrunner (Soon to have a diesel)

CRAP! The alternator tested fine. The shop I went to worked on it for over a hour and found nothing wrong with it. All they could suggest is check the wiring.

So I'm stumped again!

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2006 Jeep Liberty CRD /w GDE ECO Tune

1998 VW Jetta TDI

1995 Pontiac Sunrunner (Soon to have a diesel)

Sounds like it's time to WD40 a bunch of connectors. I recently fixed a Dodge PU by spraying the ecm connector and bulkhead connectors through the fire wall. It was running like crap and stalling. The owner spent a fortune on TC, complete tune up and alternator before that fix. Go figure.

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2006 Black Jeep Liberty CRD Limited
K&N, Samco Hoses, Michelin 245/70-16 LTX A/T2, Fumoto F-102, V-Force Muffler, Mopar, Hitch, Trailer Wiring, Skid Plates, Slush Mats, Rear Shelf, Predator Stage 1, Transgo, ORM & CodeReader, Facet 40109 Pump
"IT'S A DIESEL THING, YOU WOULDN'T UNDERSTAND"
Certified Services Auto & Truck Repair

She's up and running! It was the alternator all along!

Made a call to GDE and they set me straight. The computer only tells the alternator to turn on. There is no frequency. So what I was reading was just loose connection to my meter. The alternator has a internal regulator. So it's just like any other one!

The grist guy I took it to must of tested it wrong. I visited a different shop for a second opinion and the alt was only putting out 12 amps. So I got a new one and it's running great!

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2006 Jeep Liberty CRD /w GDE ECO Tune

1998 VW Jetta TDI

1995 Pontiac Sunrunner (Soon to have a diesel)

How many miles on your rig. It's hard to believe that two alternator went bad for no reason.

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2006 Black Jeep Liberty CRD Limited
K&N, Samco Hoses, Michelin 245/70-16 LTX A/T2, Fumoto F-102, V-Force Muffler, Mopar, Hitch, Trailer Wiring, Skid Plates, Slush Mats, Rear Shelf, Predator Stage 1, Transgo, ORM & CodeReader, Facet 40109 Pump
"IT'S A DIESEL THING, YOU WOULDN'T UNDERSTAND"
Certified Services Auto & Truck Repair

I only have 41k miles. Thats what i thought was odd. I guess it could be since the alternator is mounted on the far edge of the engine that it must get shacken up quite a bit.

Or i have a short somewhere thats taking a lot of current? I should see if i can borow a DC clamp on meter from work and read the current draw.

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2006 Jeep Liberty CRD /w GDE ECO Tune

1998 VW Jetta TDI

1995 Pontiac Sunrunner (Soon to have a diesel)