HELP: flickering headlights
I have a 2005 X5 3.0i with non-xenon (halogen) headlights that use H7 bulbs. In the last several months, I began to notice that the headlights were flickering (pulsing) back-and-forth while driving; and thought that the light bulbs are going bad. I did not change the light bulbs immediately because of the long daylight hours in summer time in Minnesota (hence did not need to turn on the headlight much).
So the dark cold winter comes and I finally got around and buy a pair of H7 light bulbs and pop them in. The headlights still flicker...
Since my car is under CPO warranty, I did not want to mess it around any further. Took the car in and was hoping that dealer will take care of it.
Any two separate visits to two different dealers; including conversation with BMW NA, I was told that the heated seats in X5 will cause a surge in current draw and that is normal and no need to fix anything. They said there is a TSB for it and all the electrical system in my car tested ok.
However, the headlights were flickering even when the heated seats were not on - has anyone experience this at all?
Anyone out there experiencing similar problem? Thanks in advance.
Traditionally, I'd say alternator
Back in the old days, when your headlights would pulse like that, it usually was an alternator problem.
Does the flickering change with engine RPM?
How much longer does the CPO warranty last?
Maybe they are hoping it will fail out of warranty.
I presume they tested the alternator and the battery, right?
Ask to see the TSB on this. If the lights are flickering without the heated seats on, something is up.
I'd suspect the alternator.
I'm not too surprised the warranty monkeys can't figure it out, though. Excuse me, I meant to say "highly skilled and trained dealer service technicians"
Re: HELP: flickering headlights
Before anyone sends you down a long and speculative path, let me tell you that this is absolutely common in the X5 without XENON. We own a 2005 also, and it has existed since day one. It is particularily annoying on dark back roads, where it becomes ever more apparent. Ours was bad enough that you could actually notice it in a lit parking lot if you were really paying attention. We also had our BMW dealer and the BMW service representative look at the vehicle, and no one denied that it was pretty bad. In the process of trying to resolve, we tested voltage at the headlamp assembly and it does indeed pulsate - particularily with seat heaters on. We tried a high capacity battery, as well as a battery (Optima Yellow) that is often used in cars with high end audio installations (Everyone swore it would help). The alternator tested fine. At least the dealer did make a big effort for us - I give them a lot of credit, but nothing worked. This was 4 years ago. In the end, we lived with the vehicle but could never get used to it. I am not kidding you, just yesterday we installed an aftermarket XENON kit just to see what would happen. The thought was that the digital ballasts (input voltage 9-16 volts) might be able to smooth out the "winking" as we liked to call it. At first, the HID kit would cycle the drivers side light on/off or turn off completely after a bit of operation. Taking advice from the installer, we put in a capacitor (designed to eliminate the bulb out warning on many cars) and that did the trick. I drove around for an hour tonite with absolutely no flickering, no winking, just pure bright light. I can't comment on the quality of the kit I purchased (It's been in the vehicle for less than 30 hours) nor can I comment on how well the kit might hold up with the voltage fluctuation. So I bought a kit with a 2 year warranty and we'll see how it goes from here. If I have to change the kit and/or bulbs every month, I will of course go back to my flickering halogens. If I get a few years out of the kit I will be insanely happy. Now my eyes can focus again!
Ripple Voltage, an explanation
BTW, Crutchfield has these types of capacitors. For the boom-boom stereo set, who add huge electrical loads to their cars with aftermarket amps and audio/video, the same kind of problem can occur. Electrical load exceeds the capacity of the alternator, pulling down voltage to the point where the ripple from the diode bridge becomes apparent and can cause lights to flicker or audio equipment to malfunction.
Again, this is an alternator problem - in the design, in this case. BMW may say this is "normal" but it is probably the result of an under-designed alternator. Replacing the alternator won't cure the problem, unless an upgraded high-output unit was used. I am not aware of a higher-output alternator made for the E53, other than the water-cooled job on the V-8 models.
The air-cooled unit on the 3.0 is probably already at max capacity (BMW alternators are designed right to the edge, it seems, hence the heroic cooling efforts needed for them, through air ducting or water-cooling. This is due in part to tighter engine compartment sizing and also to smaller, lighter weight alternators and also the huge electrical loads we have today. We've come a long way from the 35 Amp Delco one-wire of 1968. Today, many cars require 65, 90 or over 100 amps of alternator capacity!).
The HID lights use less juice than the standard headlights, so likely that's what it isn't a problem with those (that and the nature of how they work may make them less susceptible to ripple voltage).
A large capacitor will even out the voltage more and thus reduce ripple. Back in the day, power supplies for computers had huge electrolytics (capacitors) the size of beer cans (and by that, I mean 22 ounce kind) to reduce unwanted ripple voltage. Since then, power supplies have become more sophisticated and the large electrolytic "can" is a thing of the past.
It's an old-school approach, but it usually works when trying to fix a ripple voltage problem.
I know too little about capacitors
I should have put one in my 750. Maybe it wouldn't have helped. It came with a boom box, I bought from an NFL guy. 12 inch subwoofer. Turn the volume up and the lights dimmed every time the subwoofer boomed. It was kind of fun, but turn it on without the engine running and the battery would be dead in 20 mintues.
Grasshopper learn from Master!
I had a few of those clunkers myself.