What's with the L400 Hi/Low headlight combo?

[Drumster]

One of my low beams went out a few weeks ago; hi beams were both still OK. I removed the offending part, which was the larger bulb in the outer section of the headlight module... or pod or whatever you want to call it... and bought two higher grade replacements from Lordco. The new ones are 55/65 watt; hi/lo respectively, (I assumed). Result: highs and lows work fine; all is well in headlight land.

But here's the thing: Those two bulbs have two filaments each, which I would naturally expect to be hi and low. If that's the case then what's with the second bulb in the pods, which is smaller and located 5 inches or so inches to the inside of the each bigger bulb? They're a much smaller bulb and according to my observation are what comes on when you switch to high beam.

So if the two filaments in the large, outer bulb are high and low, then why does the other, smaller bulb come on in high mode and what are those other two filaments doing then, anyway?

There's no problem here of something not working; I'd just like to understand what's what. If the small inner bulb is actually the high beam, as it appears to be, then what's the second filament in the main bulb for?

If anyone can explain who this works, I'd really like to know. Call me Curious George!

Thanks!

[luckydad]

After reading this post, i tried the high beams on my L400 last night in front of a glass storefront. When I flick the high beam switch, the high beam on the outer pod do become brighter and the ones on the inner pod also goes on bright at the same time. Only thing I could think of is that this is probably the way they designed the high beam light system of our rigs. And I like it as its really bright.

Phil

[Drumster]

After reading this post, i tried the high beams on my L400 last night in front of a glass storefront. When I flick the high beam switch, the high beam on the outer pod do become brighter and the ones on the inner pod also goes on bright at the same time. Only thing I could think of is that this is probably the way they designed the high beam light system of our rigs. And I like it as its really bright.

Phil

Yes, I think you're right Phil. I haven't had a good reflecting surface to check with, only a parkade door, which gives a pretty indistinct impression. But I can't see any other explanation: Hi-beam must not be just one filament; it engages both the second filament of main bulb, PLUS a separate, second bulb.
Cheers!