2004 Discovery 70k miles. Just had the passenger side low beam and front round amber running light go out at the same time. The rectangular side running light and higbeam are still fine.
It seems odd that the two lights went out at the same time. Also have a turn signal switch problem- recently I started having the "delay" described in other posts. Since the headlight switch is on the same lever, and I'm guessing the turn signal switch is going out, could the headlight issue be related? Might it not just be the bulbs, but the whole switch itself?
Now I did have another issue happen a month ago. My wife, while backing up, somehow caught the entire composite pass. headlamp on a low tree branch and it ripped the whole assembly out, breaking the plastic retaining clips and seperating the wiring plug, causing the headlight to fall to the ground.
I popped it back in with the help of zip ties, getting it to fit pretty snug, but maybe not perfect. All lights have worked fine until now. My thought is that maybe some excess vibration over the last month has burned out the two bulbs? Just another possibility, but I'm thinking the forementioned is more likley.

 

Check your fuses, I believe you have 4 fuses and possibly a relay that can fail.

 

Thanks Mike, I saw the seperate fuses for low and high beams and for right and left sides, but unfortunatley the fuses aren't blown.
So last night I did the "hit it" test- you know, bang the problem item against something hoping for a miraculos fix- and sure enough the front round amber running light came on. Shortly after however it went out again. Banging never helped the low beam though. This reminds me of my 1965 VW Bug, where a headlight wont work until the retaining screw is snug enough to create the proper electrical ground. I can't imagine that a 2004 LR headlight would behave in the same way, but now I'm thinking that beacause the composite headlight assembly isn't fitting quite right since the plastic holding clips had broken, forcing me to jimmyrig it with zip ties, that maybe there's a grounding issue? The wire harness seems snug too, but maybe the force from having the light yanked out by a tree branch might have compromised it also? The electrical connecting pins seem straight enough.

 

anyone? Sorry guys I really want to figure this one out w/ out going to the dealer. Thanks!

 

So your wife popped out the headlamp, it hit the ground, and you are wondering why 2 bulbs failed?

You need to check the sockets at each of the bulb connections. Something got jarred loose. Wheck the wiring goin back. Actually feel the wires. It may have pulled the copper conductor apart inside the insulation. Feel for bumps and thin spots.

Oh, and if you can swap headlights from side to side, this will tell you if it is in your headlamp assembly of the wiring leading to it.

 

Ok, me stupid. It was simply the bulbs, thankfully not the wiring. Of course halogen bulbs are fragile and susceptible to failure when jarred. I'm sure the flimsy looking filament inside was engineered that way. Profitable business- about $40 for two new Sylvania H7 bulbs at Kragen auto parts. There has to be a better built, longer life alternative to halogens- LED's? I know some are using HID lighting here. Are those Xenon bulbs, and do they last significantly longer?

 

Advertised life of a xenon HID bulb is 3200 hours. Halogens last 800-1000 hours. Just a slight difference in life span between the 2 bulbs. I also ran the Sylvania bulbs (Silverstars) and loved them until I upgraded to my HIDs. Color of the Silverstar is very close to my HIDs but light output is no where close.

Any bulb is going to fail if it hits the ground. Also make sure not to touch the glass when installing any kind of headlight bulb, halogen or xenon. The oil from your skin will also dramatically shorten the life of a bulb.