2006 XK8 with 122,700 miles....

During a 20-mile drive two days ago just to exercise the car, the instrument panel lights flickered very softly throughout the entire trip. The car's performance was completely normal in every other way....

Yesterday while moving the car around in the driveway, the intermittent flickering was gone....

During a 12-mile drive to the post office just a few minutes ago, the intermittent flickering was present throughout the entire trip. When I returned home I shut off the engine, removed the key, waited 30 seconds, inserted the key, and started the engine. The intermittent flickering was gone....

No warning lights on the dash, no OBDII codes other than the normal P1111, the proper Bosch AGM battery installed in July 2018 continues to perform as it always has, the factory Denso alternator was refurbished in July 2018 with the proper Denso kit, both convertible windows drop and return as designed whenever the doors are opened and closed....

Anyone encountered this issue before? I will check the tightness of the battery cables on the battery terminals and the main power distribution module cables at the back of the trunk behind the spare tire, but the fact that this is an intermittent issue I noticed just two days ago makes me wonder if it may be something like the factory ignition switch getting flaky....

 

Jon89, not familiar with this but would you describe it the same as when you turn on something that consumes a lot of current? Resetting windows for example, window all the way up, holding button down, before the circuit breaker kicks in, lights dim a bit.

John

 

I would describe it as very soft yet steady flickering, perhaps 4 to 5 times per second when it is happening. As noted, this flickering is intermittent....

 

Hi,
The only time I have experienced lights flickering, it was associated with a failing alternator. You can check the voltage under varying load conditions to rule in or out this scenario.

All the best,

Jerry

 

Good point Jerry. When my alternator started to go, voltage fluctuated.

Easy test diagnosis at autozone.

John

 

Thanks for the advice. I would think that the alternator refurbishment done in July 2018 would still be holding up (particularly as little as this car has been driven since then, less than 1,500 miles per year), but that is certainly a possibility. I plan to check the battery cables and power distribution module cables this weekend and I will also break out my free Harbor Freight ohmmeter to read the voltages....

 

Update:

I have been too busy with other projects to get back to this strange issue until an hour or so ago. Started the engine, let it warm up for 30 seconds, no dashboard lights flickering at all. So I took the car on a 10-mile exercise jaunt and encountered no issues and no flickering. Brought the car home, grabbed my Harbor Freight multimeter, opened the hood, and checked the voltage at the two engine bay terminal locations (one on the driver side, one on the passenger side) with the engine idling. Both locations showed a steady 13.5 volts....

I shut the ignition off, removed the key, waited about 60 seconds, then started the engine again. The dashboard lights flickering was back. I decided to get out of the car and check the exterior lights to see if they were flickering as well. They indeed were. The low-beam headlights, parking lights, tail lights, and license plate lights were all flickering steadily. I let the engine run for a couple of minutes before shutting off the ignition and removing the key....

I waited another 60 seconds, then re-started the engine once again. This time, no flickering inside or outside the car at all....

This is indeed strange. Any new ideas on what to check now?

 

Jon, good one. I can't imagine how this can't be the voltage regular.

I'm not even gonna ask how you can see the dashboard lights in the daytime:-)

Jon if it was my car I'd ask autozone to run a test.

I'd try to stress the charging system to see if anything happens. Everything on at idle. High beams, rear defrost, blower on high all at idle. Best if engine hot - something is causing the swing; heat a common culprit.

There's got to be some common denominator that starts the flickering. I've never heard of a swinging failure on a diode, solder connection yes.

You know as I typed that I remembered- the test at autozone puts the charging system under load. Hey if you see a flickering have that voltmeter handy.

John

 

Thanks for your input. I also wondered about the voltage regulator after I saw the exterior lights flickering yesterday. I assume the voltage regulator is part of the alternator, correct?

I can see the dashboard lights in the daytime when the car is parked in the shade or driving underneath a tree-lined shady spot on the road....

Could a flaky relay be the source of my issue? If so, which one(s)?

 

Jon, I think the regulator is external to the alternator, so not a easy fix to get at it, but better that the removal.
I'll have to hear from the experts on this, but it sure looks to be the culprit.
As for a relay, there would have to be more than one involved with everything doing a flicker.
You did good to find that out.

 

Agree with Wayne. Jon, as soon as you described multiple circuits doing this, it eliminated relays, which by their nature would be on / off since they break the circuit.

John

 

Update:

Just spoke with the owner of the shop that refurbished this alternator back in July 2018. He says that the probability that my intermittent issue is being caused by a flaky voltage regulator is 99%. He also said it is quite unusual for a voltage regulator to begin getting flaky after just 3+ years and less than 5,000 miles. He will open up my alternator and install a new voltage regulator for around $40. I think that is a fair offer. Now I just need to find the time to pull the alternator and take it to him in Burlington (about 40 miles west of me). Since this car is now just a toy and I have other more important projects on my plate right now, it may have to wait its turn....

 

Jon,
we looked at this back when you were removing the alternator and having trouble getting the plug out (it is a bear). Here's a pic of the regulator, and of the back of the alternator a couple of posts down:
https://www.jaguarforums.com/forum/x...2/#post1925940

 

Jon, 1st disconnect the battery, then remove the bolts attaching the alternator to the mounts. Once these are out and the alternator is loose, it can be turned to access the wires and connectors. One has to hold the alt. suspended to gain easy access to the connectors; when connectors are removed, one can remove the alternator out with only the air box removed, IF you find the 1 position that allows the removal without more items being removed. Took us several different tries but it came out. Older XK8's with the noise suppressor capsule require additional items to be removed. Good Luck Friend.

 

Michael,

Many thanks for finding that thread above. I well remember fighting with that rearward-facing alternator electrical clip back in July 2018. Re-reading the thread reminded me that I simply flipped the alternator around once we had the bolts off of it and then unplugged that pesky clip....

My small-handed neighbor who helped me do this job back then is willing to do so again. He and his wife are on a hiking trip in Utah for the next couple of weeks so the job can wait until he returns. That will give me the opportunity to check and tighten up the battery cables and power distribution module cables in the trunk and hope that will fix the issue. Given my luck lately, I do not expect that to happen....

 

Possible issues with: Serpentine belt, idler pulley(s), harmonic balancer? Just to be a trouble maker, though any of these should be easier to fix than the alternator.

 

Anything is possible of course, but everyone thus far has honed in on the voltage regulator (including the guy who refurbished the alternator in July 2018)....

 

Update:

I found the time this morning to clear the trunk and check the tightness of the battery terminals and power distribution modules behind the spare tire. While both battery clamps were indeed still tight enough on the terminals to prevent me from being able to rotate them at all, I was able to tighten each 10mm nut by perhaps a half-turn (which seemed insignificant to me). The power distribution module feeds were tight as always. After tugging and pushing on them for a few seconds I determined they were fine. So I put everything back in the trunk, started the engine, and observed the dashboard lights. No flickering at all. I let the engine warm up for about 60 seconds, then took the car on a 20-mile exercise jaunt. No flickering at all. Upon returning home I put the transmission in Park, let the engine idle, then got out and did a complete walkaround to verify that no exterior lights were flickering. All exterior lights were normal....

Perhaps my tinkering in the trunk fixed any electrical connection issues that may have caused this issue but I know it is too early to declare victory since this has been an intermittent issue. I will continue to exercise the car a couple of times per week while watching the interior and exterior lights for any additional flickering. A flaky voltage regulator remains a distinct possibility but having it replaced right now is still somewhat premature in my opinion....

Any additional areas to check at this point? And is there a way to test just the voltage regulator itself?

 

Jon,

Looking for an update. Did fiddling with the battery terminals fix your issue for good? I'm having the same issue, kind of in the same situation too with a 9 month old AGM battery and a five year old, but maybe only 5,000 mile rebuild of the original alternator. But charge voltage was wavering between about 12.8 and 14.1 so I went right for the voltage regulator and threw a brand new alternator on it to no avail (ordered a new one from Amazon because my local alternator/generator shop now has about a three week wait list). Then I pulled a battery from another car and tried that. Seemed to fix the issue, but I didn't drive around with the alternate battery because it doesn't really fit the space and didn't want to mess with trying to figure out a way to tie it down. After I put the Jaguar's AGM battery back in, everything seemed to be fixed and I assumed that it was just an issue with the positive connection (I had only disconnected the negative during the alternator replacement). But a week later, driving home this evening after dark, the lights started flickering again. So I kind of think I've ruled out the battery connection. And there's not a spec of corrosion anywhere. Its dry as a bone here where I am, its an indoor car and as far back as I can remember, I don't think its even been rained on, but I did visually inspect the engine to chassis ground strap underneath which appears to be fine. I too am trying to figure out what's the next step in diagnosis.

 

The usual thing that causes the voltage to vary is that the brushes/slip rings are worn so they dont make contact all the time.
If an alternator is refurbished often the slip rings are skimmed reducing the diameter and hence the life of the brushes. Eventually, they will loose contact and the warning light will come on.

Slip rings run at up to 12000 rpm