Strange headlight issue

[CMGRover]

I've noticed the past few days that when after shutting the LR3 off, the left headlight (driver's) doesn't stay on with the headlamp delay feature. At first I thought the bulb was bad, but that's not the case, if I press the LR button on the key (I have it set to turn the lights on) both lights come on and when driving/every other circumstance they both work. Just when it's shut off and running off the delay the drivers one doesn't turn on. Any thoughts?

 

[rovernut]

Have you tried turning the feature off then back on again to see if it clears up the issue?

 

[CMGRover]

This morning the headlight didn't even come on, so it's the bulb I bet. Ordered one and it should be here tomorrow.

 

[Houm_WA]

Halogen or Xenon?

 

[CMGRover]

Xenon.

 

[Houm_WA]

How much did that bulb set you back?

...and curious how many miles. I got some feedback from some designers at Freightliner who said they'd gotten about 12,000 hours MTBF out of their HID Lighting systems. I've always wondered how that correlates to mileage. Of course light useage per mile would matter and I tend to use them less frequently, so...

 

[morrisdl]

MTBF is rather inappropriate when it comes to real world use of any arc lamp system. The number of power cycles is the most detrimental to lifespan. ESPECIALLY a power on->off->on cycle while the bulb is hot. The electrodes take a beating during the initial arc, and if they are already hot its takes 100s (maybe 1000s) of hours off the life span.

 

[Houm_WA]

Yeah...I suppose I agree with you technically. For certain with arc lamps the biggest factor to them finally failing is the cycling, which is why I try to avoid doing that. I only turn them on when I know I need them and that I'm going to leave them on.

That said, it would be VERY difficult to determine such a statistic unless you are really trying to, and you tracked it from the beginning. I am merely reporting what I learned from an Engineer at the heavy truck manufacturer. Of course 12,000 hours MTBF is gonna vary greatly depending on how people use their lights, because really as you point out, that number is loosely correlated to how many times the headlamps are cycled over time.

 

[morrisdl]

As a data point - In out network operation monitoring center, we have 4 projection TVs. 2 of them are on 24/7 365, and the other two are turned off nightly. The two that are power cycled nightly, the bulbs are replaced 3 times per year (@$450 ea). The two projectors that never turn off are still on the original bulbs 18 months and counting. These 24/7 projectors are ~10% dimmer than the ones with the new bulbs, but still.

The LR3 auto headlight function is great, but it everything I pull into the garage it fires up the headlights for <10 sec. Wish it was a little smarter somehow.

 

[Houm_WA]

Yeah....that's why I don't use the Auto function!

I do; however, use it on our Q50 because its headlights are LED.

@CMGRover: Before this Geek-Discussion ensued, I'd asked about the price of a new bulb. You don't happen to recall off the top of your head do you? Thanks.