Pulsing lights giving me a headache

KeighJeigh · **Posted:** Sat Feb 26, 2011 1:59 am

I've noticed this for the past year or so: Headlights and interior lights dim when I let off the accelerator & then recover. I've seen this in other cars but it's fairly significant with my 05 and my wife's 06 doesn't have this issue. However, far more annoying (and I assume is related) is the pulsing in the headlights when I turn on the fan, operate the windows or other large power draw. Sometimes hitting brakes will do it too. It isn't a flicker because they never go out - it's more of a rapid but steady pulsing of perhaps 2-3 cycles/second. I can see it in the cabin lights as well.

I've swapped out the optimus battery (ouch$) thinking it might not be charging fully & perhaps constantly taxing the system . . . .but nope. I replaced the alternator a couple years ago but figured that would either charge or not charge. (which it why I replaced it) It appears to put out plenty of amps because I can crank on everything at idle and it wil dim, but then appears to recover.

Strange thing: It doesn't always do it. Sometimes when idling with heavy loading it's steady, but when I rev it up the lights usually begin to pulse as I pass through 1,500 rpm or so, then less pulsing at 3k, but still there. However, I do not notice it at 3k rpm while going up a long hill.

Strange issue but I would like to fix it before getting stranded during one of my midnight logging road adventures.

BlackLibertyCRD · **Posted:** Sat Feb 26, 2011 11:04 am

It's the alternator doing that or a loose connection at the alternator.

painemann · **Joined:** Sat Dec 20, 2008 7:02 pm **Posts:** 607

I also have this problem and I know of a few others who have been dealing with it. I have a new battery but have not tried a new alternator yet. I don't think mine is as severe as yours is but I do notice it and it is annoying. When the hvac fan is on high it is much more consistent.
I'm sure some others have this issue and will chime in. Maybe someone has fixed it.

painemann · **Joined:** Sat Dec 20, 2008 7:02 pm **Posts:** 607

BlackLibertyCRD wrote:

It's the alternator doing that or a loose connection at the alternator.

I know it's not a loose connection at the alternator. Maybe our jeeps need a more powerful alternator then the factory one!?!

papaindigo · **Posted:** Sat Feb 26, 2011 2:17 pm

I'm not the greatest auto electric person on anything like today's computer driven vehicles but in the olden days, up into the early 1970s, I'd be looking for an alternator problem or voltage regulator problem or both especially if the battery is relatively new and tests good. A good specialty local auto electric shop, not the dealer or your regular auto shop, should be able to locate the problem fairly easily. FYI the KJ voltage regulator is built into the PCM (Powertrain Control Module - see pg 8E-16 of the 2005 factory service manual; Note this is NOT the ECM or Engine Control Module) and cannot be serviced separately like they could in the past.

PS - see GDE post below for correction to FSM

Billwill · **Posted:** Sat Feb 26, 2011 2:26 pm

What about the one-way clutch(or whatever it is called) on the alternator pulley? They are known to give a lot of problems according to what I have read on the various KJ Forums.

warp2diesel · **Posted:** Sat Feb 26, 2011 5:33 pm

Hook up a volt meter to the power port or a live wire in the fuse panel you see when you get into the left side front door.
My wife's TDI pulled had a bad connection cable between the alternator and the power distribution center. Even with a hydrogen gas free Optima, we have had a rough winter in most places and if salt is used on the roads to melt ice, it can screw up the connections. Lots cheaper than replacing the alternator first if it is the problem.

KeighJeigh · **Posted:** Sat Feb 26, 2011 7:05 pm

I'm beginning to suspect control module issues of some sort. It's almost as if the regulator is flipping back and forth - turn on full, turn off, turn on full, turn off. When the load gets high enough to warrant pulling from the battery, it kicks in full to prevent that from happening, but then it thinks "wait, the battery is charged, I don't need to be on this much" and kicks off again and so the cycle goes. (This is an anthropomorphic view of the alternator and only describes its actions. I don't actually know what's going on)

Since this is no longer the era of soldering irons and duct tape on my old Ford Maveric, and since any carpart with the word "module" tends to be very expensive, I'm inclined to fiddle with it as much as I can to determine what it is before replacing or taking it to the stealer.

° Never seen salt corrosion issues here in Western Wa.

° I checked all the connections, but I don't think a loose connection would cause perfectly sequenced pulsing. It doesn't flicker on and off, it pulses 2-3 times per second .

° I've had the clutch/pulley issue before and replaced the pulley. That problem created an obnoxious racket and a redish dust all over the place, but didn't affect
the alternator until it finally broke.

° Since others are experiencing the same thing, I'm thinking it is probably a solid state issue.

Hmmmmmm.....

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The service manual is not correct regarding the voltage regulator for the 2005/2006 Liberty CRD. The alternator is self-regulating and all the engine controller does is send a "wake-up" message at start up to turn on the regulator. Even if the wake-up does not occur the regulator will turn on the alternator when the engine exceeds 1000 rpm.

geordi · **Posted:** Sun Feb 27, 2011 7:09 am

The alternator IS doing it's job correctly, the problem is that the alternator PULLEY is not. The clutched pulley is failing. You can replace just the pulley for $60 or so in parts (and a PITA job pulling it) or get an entirely new alternator with the correct clutch for $150 with a lifetime warranty from AutoZone or Advance Auto. They DO have the correct clutch pulley on them.

FYI: I had this exact same problem, and swapping the alternator / clutch was the instant fix. The problem has NOT returned in over 40k miles so far.

KeighJeigh · **Posted:** Sun Feb 27, 2011 11:25 pm

geordi wrote:

The alternator IS doing it's job correctly, the problem is that the alternator PULLEY is not. The clutched pulley is failing. You can replace just the pulley for $60 or so in parts (and a PITA job pulling it) or get an entirely new alternator with the correct clutch for $150 with a lifetime warranty from AutoZone or Advance Auto. They DO have the correct clutch pulley on them.

FYI: I had this exact same problem, and swapping the alternator / clutch was the instant fix. The problem has NOT returned in over 40k miles so far.

Thanks Geordi,
I went through the clutch/pulley fiasco a couple years ago and replaced it. But for me at the time the symptoms were a loud rattling racket, the weird dust and vibrating belt. I didn't see light pulsing at the time.

geordi · **Posted:** Mon Feb 28, 2011 12:40 pm

Hey, no worries. I was getting driven nuts by the pulsing too, and decided to give changing the pulley a shot.... Until I managed to strip the center 10mm shaft by turning it the wrong way like an idiot. Thats when I pulled the whole thing and swapped it at Advance. Now, if it does that again... The whole thing goes back and I get a new one free. Can't beat that!

painemann · **Joined:** Sat Dec 20, 2008 7:02 pm **Posts:** 607

geordi wrote:

Hey, no worries. I was getting driven nuts by the pulsing too, and decided to give changing the pulley a shot.... Until I managed to strip the center 10mm shaft by turning it the wrong way like an idiot. Thats when I pulled the whole thing and swapped it at Advance. Now, if it does that again... The whole thing goes back and I get a new one free. Can't beat that!

I stripped that shaft also! So I just used an impact to "snug" it up, worked but I think I over tightened it and it needs to be replaced again. So I guess my pulsing problem could be caused by the pulley! thanks for posting time for an new alternator!

KeighJeigh · **Posted:** Mon Feb 28, 2011 10:37 pm

But how could the pulley be creating a seemingly timed pulsing of the lights at a variety of rpms - especially when I didn't see it last time the pulley went bad. (And there are none of the other bad pulley symptoms) I would think it would be more pronounced at idle, but it's not. Also, it's spinning so fast that even if the pulley was bad, I don't see how the speed of the alternator could possibly be fluctuating dramatically or rapidly enough to cause this.
Perhaps I'm wrong, but I just hate the idea of wrestling with that amnday pulley again if it's not the actual issue.

BlackLibertyCRD · **Posted:** Mon Feb 28, 2011 11:03 pm

The pulse and weakness of your alternator is probably caused by a bad diode. There are six diodes that act as a check valve in the alternator and if one is burnt out the electric current would blink each time its turn came up to allow electric current to pass through. :wink:

KeighJeigh · **Posted:** Tue Mar 01, 2011 12:02 am

BlackLibertyCRD wrote:

The pulse and weakness of your alternator is probably caused by a bad diode. There are six diodes that act as a check valve in the alternator and if one is burnt out the electric current would blink each time its turn came up to allow electric current to pass through. :wink:

Makes sense.
Do you happen to know if they are accessible such that I could hook up my multimeter to each one separately to test?
And ultimately, solder a new one in . . . From what I've seen, these alternators are none too cheap.

geordi · **Posted:** Tue Mar 01, 2011 1:55 am

That is actually a very good explanation, and tells me that even if I hadn't screwed the shaft on mine... It wouldn't have fixed the problem.

As for forking about with a multimeter in these things, I don't know if that would be worth the effort unless you happen to also be an experienced alternator repair shop. The diodes are liable to be fairly large, owing to the amount of amperage that these things have to produce. If only ONE diode at a time is cycling, then you are putting upwards of 1kW through it. Thats a fair bit of juice at low voltage. Sourcing something like that isn't gonna come from Radio Trash, methinks. Then there is the problem of matching the existing part...

Why screw with it, when the lifetime warranty is only a single purchase (at half the dealer's non-warranty price) away?

maxf15 · **Joined:** Tue Feb 28, 2012 1:30 pm **Posts:** 52

Okay, so I've had my 2005 Libby for exactly a month and I'm having the same problems. Hardly ever drive at night so I only noticed the pulsing of the headlights/interior dome lights then.

No sluggish crank, or weak power issues. (I got it with a non-Optima replacement battery. FYI.)

So as I read all the comments, it sounds like I need to first check connections, then have the battery/alternator checked, and prepare to buy a new alternator!

This forum is King-Kong! Nice to tap into all y'all's (yup -that's a word down here in Georgia) corporate knowledge.

Will post results.

KeighJeigh - Would really like to hear what finally worked for you.

Thanks.
_______________________________________________________________________________________
2005 Liberty Sport 4x4 CRD: ORM, EHM, Samco Hoses, MAP cleaned, B100, Wix FF, 85k miles

geordi · **Posted:** Fri Apr 06, 2012 10:43 pm

Where in Georgia?

As for the problem of pulsing lights - The voltage regulation is handled entirely in the engine computer by rapidly "flashing the field" of the alternator itself - rapidly cycling the power field of the alternator on and off, and varying the input voltage in the field to make different output levels. What this means is that the alternator itself is somewhat of a dumb device, only doing what it is told and spinning along merrily... Except for the internal diodes and contacts. If you are having pulsing light problems, it is due to either a slipping clutch or a blown diode. Either one is a pain in the arse to deal with, when a full replacement alternator is $150 from AutoZone with a lifetime warranty and will, without question, solve this problem.

If the diode is the problem, wouldn't you want a fresh clutch anyway, after so many miles of spinning and clutching? I would.
If it is the clutch... Well... Wouldn't you want a fresh set of diodes anyway, since they do also go bad? Yep, I would.

Best of luck to you.

Billwill · **Posted:** Sat Apr 07, 2012 3:57 am

geordi wrote:

Where in Georgia?

As for the problem of pulsing lights - The voltage regulation is handled entirely in the engine computer by rapidly "flashing the field" of the alternator itself - rapidly cycling the power field of the alternator on and off, and varying the input voltage in the field to make different output levels. What this means is that the alternator itself is somewhat of a dumb device, only doing what it is told and spinning along merrily... Except for the internal diodes and contacts. If you are having pulsing light problems, it is due to either a slipping clutch or a blown diode. Either one is a pain in the arse to deal with, when a full replacement alternator is $150 from AutoZone with a lifetime warranty and will, without question, solve this problem.

If the diode is the problem, wouldn't you want a fresh clutch anyway, after so many miles of spinning and clutching? I would.
If it is the clutch... Well... Wouldn't you want a fresh set of diodes anyway, since they do also go bad? Yep, I would.

Best of luck to you.

Not quite correct....if you read Keith of GDEs' explanation above you will see that the 05 upwards KJ has a regulator built into the alternator as was done in the old days...the ECU only "wakes up" the regulator.

I believe the problem is firstly the clutch on the alternator or a faulty regulator....I do not buy the idea of a blown diode in the diode pack causing the flickering....the alternator runs at such a high speed that one would not see the effect of one rectifying diode being blown.

I would also check for good earthing straps of engine to chassis and of course good battery connections.

Pulsing lights giving me a headache

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