This problem is most likely electrical...easy...tracing it backwards..not so easy. I suggest tracking the wiring backwards from the headlights since they seem to be involved. The headlights are connected to the system through a relay that goes to the body processor. I suggest at this point that you pull the connectors to the body processor and the ECM and spray them down with electronics spray. You couold have a bad ECM and I am thinking this is the problem. Check both for corroded connections and moisture. I also would get the car codes read by the dealer to see if you have body, abs or tranny codes that do not show up on OBDII. If this were my car, I would at this point go into emergency mode as the car has become unreliable.

 

It's not really unreliable. It's happened twice in the six or seven months I've owned the car. The first time it happened I was a little worried, but this time simply pulling over and restarting the car cleared up the problem. Also, it gives me lots of warning. The flickering is barely noticeable at first, then it gets worse and worse over 15 to 20 minutes. The next time it happens I know that I just need to "reboot" the car by pulling over and turning off the engine for a few seconds.

I bought a new serpentine belt because when idling on Saturday I could hear the belt making a little noise. Maybe the belt is slipping on the alternator and its not generating enough electricity at times... I dunno... It's worth a try. I may never know if this actually fixes the problem, though, since it is so intermittent.

 

What about the voltmeter, maybe even a separate alternator measurement when this happens. If only you had that ultragauge thingy

 

I had something similar in some of the symptoms. It turned out to be a broken terminal on the starter solenoid. It caused a big load drop due to an intermitent connection. Sometimes it would start sometimes not. Everything went dead, but then came back to life with several warning lights lit. The harness was so tight the engine torque broke it. Worth checking it. P.S. there is a rubber boot covering it...that all looked fine until I jiggled the wire and discovered it was just touching.

 

Sam,
You mentioned one thing that intrigues me. When the latest episode happened, you pulled into a gas station, hit the highbeams, and everything died. Have you hit the highbeams since then? I'm wondering if that could be related. Maybe the light switch is bad and causing a short or something that's crashing the rest of the system. Could also be the cause of the flickering as a marginal switch could be on the hairy edge of going to highbeams, and the crash.

Also, feel around the switch for heat when turned on.

Purely speculation, but it's the closest thing you said that looks like cause and effect so far.
Mark

 

The high beams cause everything to die because they draw more current than anything else. For example, when I turn on the turn signal or apply the brake lights I can see the flickering get worse, but the high beams just cause it to flat out die.

After I restarted the car I drove several more hours at night using the high beams intermittently with no problems. This has been a twice in seven months event. In those seven months I've driven about 11,000 miles, a lot of it at night. I'm just going to chalk it up as one of those weird things that happen with these cars. I'm going to replace the belt. I checked the battery terminals. I checked the connections at the alternator. It may never happen again. If it does, I know what to do. I can't really come up with a definitive solution unless the problem shows up and stays long enough to allow me to troubleshoot it. I know what to do to keep the car running if it happens in the middle of a long trip again.

 

Oh yeah... I just remembered one other little detail. The windows lost their programming when the car cut off. Just more evidence that it's a voltage problem.

 

Sam, I hate to say this because you will say, "does that guy think I am stupid" If this were a normal American car I would swear that you have a ground problem. The reason I am reluctant to mention it is that I know that this car has some floating grounds. I have never looked at a schmatic so I can't say with certainty which grounds to check. When I had the carpet out of my car I saw four ground studs just in the cockpit. I saw one or two in the trunk. Many times American cars will have paint under a ground bolts. If I were you I would disassemble every ground I could find I would make some bare metal. I would also put some conductive paste on the connectors when it goes back together. Just an idea.

 

Sam. I just read some of the other posts. Sorry about the repitition on the ground statement. I will read before I write next time.

 

I don't think it's a ground problem because of the way it fixed itself both times. I know a loose ground could suddenly make good contact and fix itself, but the fact that simply turning the engine off and back on makes the problem go away leads me to believe that it's not a ground issue. I was thinking that maybe I had an alternator issue, but I never get an alternator light. Then I thought that maybe the belt was slipping on the alternator. The more load there is on an alternator the harder it is for the belt to turn it and the more likely it is for a belt to slip. However I would think that I would get an alternator warning light on the dash if that was happening. I changed the serpentine belt tonight just in case.

 

Jaguars are probably an exception because every problem is a weird, goofy problem. But in most circumstances when there's a weird, unexplainable electrical problem, its a ground.

 

Sam,

In most all cases when an alternator goes bad it is bad all the time not part of the time. I go with a poor connection it being power or ground. Denial and pride could become a long road to travel; however, on the flip side we could all be wrong. Not trying to be smart only trying to help!

 

I agree it cannot be the alternator. I dont think its a connection at the battery either or it would not restart. I would be willing to bet a poor connection at a fuseable link first or ground second. The next time it happens check all your electrical devises and find out which ones do not work. They will all have 1 power supply in common and that will point you to which one. keep a log and we together can fix this!

 

I believe I have resolved this problem. I had been having a couple of other voltage related issues, namely, every once in a while when I would try to start the car, it simply wouldn't crank. Sometimes the interior lights would work, the fan would blow, and the radio would work, but it wouldn't crank. If I'd wait a few minutes it would usually start. Also, my windows would lose their programming every once in a while, and, of course, I would also have flickering headlights infrequently.

I thought I might have a battery problem, even though the battery is less than a year old. The auto parts store tested it and said that wasn't the problem. Then one day when it wouldn't start I tried twisting the lugs on the battery posts. I also tugged on the red cable, and bingo, the trunk lights came on. I discussed this particular incident in another thread.

Today it happened all over again, and tugging on the battery cable got the car to start right up. So when I got home I pulled out the spare tire cover to trace the battery cable. It goes to a black box directly in front of the spare tire. I popped the cover off of the box and inside the box are two 500 amp fuses. A twist on the nuts which hold the fuses revealed that one of them was only finger tight. I tightened all of them up, and I'm 99.9% sure my problems is solved for good. If it comes back I'm just going to replace the fuses, maybe there's a bad connection inside of one.

This was one of those things that happened so intermittently it was impossible to duplicate. But once I fixed the problem by tugging on that red cable I figured that had something to do with it. And then when I duplicated the fix today and discovered the loose nut, I'm pretty sure this issue has been resolved. Only time will tell.

 

I FINALLY fixed this problem for good. No doubt about it.

Over the past month or two I was having the flickering headlight problem more and more frequently. Also, when I would go to start the car sometimes it would act as if the battery was completely dead. When I'd turn the key to accessory everything would light up as expected, but then as soon as I tried to crank it everything would just die. I learned that simply tugging on the battery cable would fix the problem. I tightened the bolt that holds the terminal to the post. I bought a wire brush and cleaned both the terminal and the post on the battery. But still the problem would come back. I could graph the voltage on my OBD tool, and it was fluctuating wildly between 10 volts and 14.5 volts. Twice within the past week I've gotten the "gearbox fault" message when the lights totally blink out. A few weeks ago I though I had a loose connection at the main fuse down by the spare tire. I tightened it, and everything seemed good at first, but then it came back.

Yesterday, the car wouldn't start. It appeared to be a dead battery again. I went back to the lug on the battery and as soon as I touched the cable I heard a snap, like an electrical arc, and all of the lights and everything in the car came on. The sound seemed to come right from the battery cable itself. So I unbolted the cable from the battery and the fuse box down by the spare tire. I carefully examined it, and there appeared to be a lot of corrosion underneath the red jacket right where it is crimped to the lug that bolts to the battery. My first thought was just to buy a new cable, but I'm sure it's not something that the local Jag dealer stocks, so I just put it in my vice and squeezed the giant crimp connector down tighter. When I put it back in my car it was like magic. The flickering is COMPLETELY gone, It seems like there has always been a very slight flickering of the headlights and instrument panel lights. Not anymore. It is rock steady. The voltage reading on my OBD tool is completely flat. It might change by 1/10th of a volt when I roll down the windows, but for the most part it is a completely straight line on the graph. I drove the car tonight and the HIDs have no flickering whatsoever.

I have no doubt that this was the problem all along. I'm going to go ahead and order a new cable, just because I don't know the internal condition of the one that's on my car right now. Apparently it was only making good contact part of the time, and that was causing my problems.

 

Just common sense... Next time it flickers, pull off to a safe spot, open car door, open hood and see if you can hear where whatever noise is being made when you flick on your high beams...

 

you stated belt sqeal on high load,perhaps serpintine tensioner is worn out...steve.

 

Nope... The crimp connection at the battery terminal was absolutely, unquestionably the problem. Now that I've re-crimped it in the vice I've had no problems at all. The voltage, as shown on the Torque App on my Android phone, has been rock steady since I re-crimped it.

The car has been running splendidly, too, by the way. It seems to have more power than ever. The shifts are smooth. I'm luvin' it! And the weather has been perfect for driving!