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pulsating lights on my liberty (moved from General)
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Author:  crdvictim [ Sat Oct 15, 2011 1:49 am ]
Post subject:  pulsating lights on my liberty (moved from General)
the lights on my 06 crd pulsate with the rpm of my engine. i have 12.5 volts with engine off. i get 14 volts minus 0.5 volts with lots of accessories on when engine running .while engine is at idle the lights are steady. when the rpm rise above 1200 to 1500 rpm the flicker/pulsing becomes noticeable. tested at battery and also at alternator output. alternator is recent maybe 7000miles. brand new red top optima is maybe 1000 miles old. connection at engine bay fuse box feed i checked and cleaned. my meters analog and digital do not register these flactuations . the lights inside the cabin the headlights and instrument cluster all pulsate meaning get brighter and dimmer like a flicker with out going completely off. it is noticeable especially at night. this problem just started and was not the initial reasons for changing the alternator or battery. i think those parts were just used up after 250 000 km of high way driving, any help / tips / suggestions / ideas would be greatly appreciated
:5SHOTS:
Author:  Billwill [ Sat Oct 15, 2011 2:54 am ]
Post subject:  Re: pulsating lights on my liberty
Do you have a good, clean, tight earthing strap going between the engine and the chassis?
Does the new alternator have a good clutch/pulley assembly and is the serpentine belt tight?
That is about all I can suggest at this stage. :?
Author:  crdvictim [ Sat Oct 15, 2011 11:30 am ]
Post subject:  Re: pulsating lights on my liberty
Billwill wrote:
Do you have a good, clean, tight earthing strap going between the engine and the chassis?
Does the new alternator have a good clutch/pulley assembly and is the serpentine belt tight?
That is about all I can suggest at this stage. :?




ok ok i will check the ground strap right after breakfast, the belt too, the alternator clutch/pulley assembly? hm. not sure about that one though. the output from alternator looks to be steady 14-13.5 volts running. how would one go about checking that? must find out. B.T.W. thanks for the tips. :rockon:
Author:  Billwill [ Sun Oct 16, 2011 12:33 pm ]
Post subject:  Re: pulsating lights on my liberty
crdvictim wrote:
Billwill wrote:
Do you have a good, clean, tight earthing strap going between the engine and the chassis?
Does the new alternator have a good clutch/pulley assembly and is the serpentine belt tight?
That is about all I can suggest at this stage. :?




ok ok i will check the ground strap right after breakfast, the belt too, the alternator clutch/pulley assembly? hm. not sure about that one though. the output from alternator looks to be steady 14-13.5 volts running. how would one go about checking that? must find out. B.T.W. thanks for the tips. :rockon:


I would suggest you move your post to the CRD section below as this problem may be relevant to a CRD only....in that that CRD uses a one-way clutch on the alternator so the experts there will be able to advise you on how to check the alternator clutch and there may be some other issues that may be relevant to your problem which may be CRD specific. :)
Author:  ATXKJ [ Sun Oct 16, 2011 4:02 pm ]
Post subject:  Re: pulsating lights on my liberty
on mine pulsating lights were a dead alternator (there's a regulator circuit built in)
but it takes the dealers scan tool to be certain - only thing i knew for sure was a volt meter oscillated 12-14 volt while driving steady speed.
Author:  Billwill [ Mon Oct 17, 2011 3:29 am ]
Post subject:  Re: pulsating lights on my liberty
When I had some charging issues on my 2002 CRD, for a while I drove around with my voltmeter plugged into the cigar socket so I could monitor the charging voltage while driving....a permanent fitted voltmeter gauge would be nice to have.
The early KJs, from about 2002 to 2005 I think, did not have regulators built into the alternator but had the PCM/ECM monitor the voltage and accordingly adjust the voltage on the alternator field coil.
Later KJs have a regulator built in to the alternator and use a "wake up" signal from the PCM/ECM to start regulating once you hit about 2,000 RPM from initial idle.
Either way, worn brushes in the alternator could be a problem although this alternator in question is fairly new.
Author:  crdvictim [ Mon Oct 17, 2011 12:25 pm ]
Post subject:  Re: pulsating lights on my liberty
once again thanks for the tips , btw ground strap is good so iam thinking perhaps the ecm/pcm is having issues???? hm seems as though a trip to local stealership is necessary. :roll:
Author:  Billwill [ Tue Dec 03, 2013 2:03 am ]
Post subject:  Re: pulsating lights on my liberty
crdvictim wrote:
once again thanks for the tips , btw ground strap is good so iam thinking perhaps the ecm/pcm is having issues???? hm seems as though a trip to local stealership is necessary. :roll:



Try asking in the CRD section below....maybe someone has an answer for you :)
Author:  crdvictim [ Mon Dec 16, 2013 11:45 pm ]
Post subject:  Re: pulsating lights on my liberty
the lights still pulsate on the liberty. I some what gave up on it but still have it on my mind. tried a bunch of things like ground straps and such. alternator de coupler is good. alternator it self is good. grounding is good. battery is a good optima. all new within two years. at one point when mucking around with the plug in for the alternator field supply the problem went away for a few days. by mucking I mean taking the plug itself apart and trying to make the metal connector tighter and cleaning it. but after a couple of days the pulsating came back. seems as though weather or moisture and temperature have some affect on the severity of the pulsating magnitude making it more pronounced. I will keep trying if its the last thing to do! :dizzy:
Author:  crdvictim [ Mon Dec 16, 2013 11:49 pm ]
Post subject:  Re: pulsating lights on my liberty
btw thanks for the e-mail billwill. not sure how to move posts around though
Author:  Billwill [ Tue Dec 17, 2013 4:26 am ]
Post subject:  Re: pulsating lights on my liberty
Looking at the circuit diagram for the 2006 CRD it looks like the alternator is the same as the previous models....it does not have a built-in regulator but gets its field coil pulses from the ECM as usual.

The Black wire on the small connector goes to ground at G111 via connector C108...there could be a bad connection in the C108 connector or the ground point itself at G111 might be bad. You could try splice in another ground from a good clean chassis point into the Black lead right near the small connector that plugs onto the alternator. You can never have too many grounds so it is worth trying this as a temporary measure.

The Brown/Dark Green wire from the small connector goes to the BCM Connector C1 pin 18 via connectors C114 and C120..you may have a bad connection here somewhere as well. The connector locations are shown in the Circuit Diagrams.

If you do not have the circuit diagrams they are part of the 2006 KJ Service Manuals...you can find the link in SAM's Noob Guide.

I personally would cut he Brown/Dark Green wire near the small connector and also cut this wire at the BCM connector C1 pin 18...in case this wire is fraying to chassis somewhere. The I would replace this disconnected wire with a temporary wire going straight from the small plug on the alternator straight to Pin 18 on connector C1 at the BCM...bypassing the connectors C114 and C120 altogether. This may sound a bit drastic but it is easy to solder the wires back in place and insulate the joins with shrink tubing. I had to do this several times to repair 6 faulty wires on my 2002 CRD!

I believe on the 2006 CRD the field coil on the alternator is activated via the BCM only when the RPM goes above 2,000 RPM at which stage the Pulsed Width Modulation pulses are applied to the field coil to increase/decrease the charging rate....this may be why there is a difference between low idle....no problem...and high idle...problem.

All of these controls and sensing of the status of the Headlight switch etc. are done inside the BCM...this is shown as a "Black Box" in the circuit diagrams so it is impossible to see what goes on in there. You can try re-plugging the connectors on the BCM or in the long run you may need to get the BCM re-programmed or replaced. :(

Do you hear the High Beam Relay...on front of internal fuse panel...chattering while the high beams are flickering?

Edit to add: I really do not trust the documentation too much as far as how the charging system works....there are so many contradictions between the Theory of Operation and what the circuit diagrams show. The Theory states that + 12 volts is supplied to the +side of the field coil from the ASD relay. The other side of the field coil is connected in series with the regulation circuitry inside the PCM to switch this other side to ground to regulate current....this is how it is done in my 2002 CRD. In actual fact the circuit diagram shows the other side of the field coil (Black wire) going straight to ground while the Brown/Dark Green wire goes via the BCM to... I presume a regulated +12 volts pulsed current supplied by the PCM.

So it is best to be very wary when following my advice of cutting the leads at the small plug and replacing them with a direct wire to ground on the one side and with a direct wire the pin 18 on C1 of the BCM...If I was there I could assertain which is correct...the circuit diagram or the Theory of Operation....I believe the Circuit Diagram is correct and that the Black wire goes direct to ground and the Brown/Dark Green wire goes to Pin 18 on connctor C1 of the BCM and that the BCM in this case is regulating the Positive side of the field coil :shock:

You need a meter capable of seeing a fluctuating voltage across both the battery and the headlights! :wink:
Author:  papaindigo [ Tue Dec 17, 2013 10:17 am ]
Post subject:  Re: pulsating lights on my liberty
If it seems weather or moisture related try some dielectric grease on the contacts to seal out same.
Author:  dgeist [ Tue Dec 17, 2013 10:27 am ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
Moved to the CRD forum...
Author:  pwrwagn [ Tue Dec 17, 2013 10:51 am ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
I have seen this happen before, but it had one of two causes... A battery with high internal resistance, or a poor ground to the computer/regulator/control module.

Since you have a new battery, it tends (but not guarantees) to rule out a battery problem. It is possible that there's a problem with the battery, even a new one - just not likely.

So, I would look very carefully at the grounding and wiring to the module.
Author:  Brianawd [ Tue Dec 17, 2013 12:51 pm ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
I have this same issue every now and then. Its seem it happens most the time, when I am running the driving lights. If I turn off the driving lights, the issue goes away. My issue is maybe once of twice a month.
I Like you have tested everything. Still have not been able to find the cause.
Author:  tjkj2002 [ Tue Dec 17, 2013 3:14 pm ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
Betting it's the battery,optima's are well known now to be total junk even when they are brand new.After 1-2 years they have a 90% failure rate since JC took over a few years ago.
Author:  65Corvair [ Tue Dec 17, 2013 9:19 pm ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
My jeep had the light flickering issue too, a new alternator solved this issue for me.
Author:  GreenDieselEngineering [ Wed Dec 18, 2013 10:53 am ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
The 2005-6 KJ CRD in North America uses a self-regulated alternator. The ecm only sends a wake-up signal after start-up once the engine is running stable. The alternator will turn itself on above a certain rpm threshold...maybe around 1000-1500. The service manual most likely was not updated properly.

The voltage spikes could be from a failing regulator on the alternator. An oscilloscope would would be very helpful to root cause the source.
Author:  ChesterCRD [ Wed Dec 18, 2013 5:05 pm ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
A friend had this going on with his CRD. The interior lights and headlights would pulse rapidly. After a year of trying different things we swapped the alternator during the timing belt service and that took care of it.
Author:  thermorex [ Thu Dec 19, 2013 1:51 am ]
Post subject:  Re: pulsating lights on my liberty (moved from General)
I have the same issue only when engine is cold and only with headlights on while Idling... Charging is OK, my money in this case is on the regulator, as Keith said. Ill have to swap it with the original one that I replaced a while back due to the clutch.
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