Okay, I bought and installed a used set of the Depo Euro lights on the SD almost 2 years ago. Love the look but more importantly they perform so much better than US spec lights IMHO. Anyway Driving home the other evening just after dusk it seemed a bulb was out. The high beams and fogs all work but the passenger side low beam was out. I checked the fuse box and cleaned the contacts for that lights fuse ( I will still replace since it is the aluminum type) and still no light. I pulled the bulb and it looks okay not burnt and the filaments look okay ( I need a magnifying glass to make sure ) Anyway I could not find them for sale here on Pelican any thoughts on where to buy ? Also since I do not have all my shop manuals ( in storage ) available does the high beam use a different relay ? Meaning should I check the low beam relay ? Also the P/N # etc on around the ring of the bulb base is really worn / faded and hard to read at all.
I think I can make out "OSRAM" ( sylvania ) but not the wattage. I believe it says 55/65 ( one bulb for high and low ) Thoughts ? I do not want to buy a pricey bulb if not necessary. I do have a pair of bulbs for the uninstalled euro lights for my 500E but again in storage.

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

Unless modified after the fact, the headlamps are not powered through relays.

No mods I just did not look too far after I pulled the bulb out. Shame though the High beam worked fine. I need to look again though unless some knows the answer. On these dual filament bulbs do both low and high beam come on when you power the high beams ? If so would an issue in the multi function control stalk possibly case the problem ? I need to replace that as well since the turn signal stalk stopped returning to the center automatically about a year ago.

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

Given that the filaments are intact, a common cause for one failing to light in W126s is a corroded or broken slipon terminal that forms the connection with the spade on the bulb. As a check of bulbs, swap left to right.

It looked to me like the high beams only power the high beams and the low beams only power the low beams.

Thanks for the info. And for the idea. I am off tomorrow and will swap the bulbs and or see if I can find my electrical tool box and put a circuit tester on it.
Not having much luck with finding a replacement bulb yet. I know they are available.

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

Okay so the bulbs are not hard to find. The ones that kept popping up for me were bulb and lenses. So after I swap the bulb in the a.m. I may bite the bullet and buy a set of the sylvania Ultra's. I have been using these in my 03 Suburban for almost 5 years and love them. Yes the durability comes into play , I think they have been lasting about 2-3 years before one or the other goes out.

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

I just had the low beams in the original bulbs I installed with the Depo lights both fail, one within a week of the other. Mine lasted roughly 19 months.

The bulbs looked fine when I pulled them out, but I have seen that previously with other H4 failures.

I no longer have a consumers union membership but as I recall, Consumer Reports tested headlight bulbs and found the gains from the pricey premium ones were marginal in relation to the elevated prices (around here, 3x to 4x a generic one).

Most packages aren't marked with the original H4 designation anymore, but 9003 instead.

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22

That sounds about right. I originally installed sylvania bluestar ultra ? and they went out in one case in less than a year. I then read some articles that said that the Ultra ones worked much better. I am happy with them even with the price. We drive a lot on back roads as well as in poor weather and I notice a huge difference in how clear the light shines as well as brightness. Now this was on my 03 suburban I hope they work as well with the Depo's on the 85 300SD.
Alan

__________________
92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

i made the mistake of buying depo brand headlamps once. never again. build quality was piss poor imo. "made in china"

Sure, quality is iffy in some areas.

The lens retainer clips and the small hardware like speednuts are awful. The electical connectors are cheap and had to be snugged up. The bulbs supplied were subpar but that was expected at the price point for the package.

OTOH, the lenses seem excellent and only a tiny sign of moisture in one headlamp after a really violent summer storm this year.

Overall, for what I paid versus what a used set of OE Bosch were going for at the time I purchased mine, I am happy. The Depos are now sellling for less than I paid, though I guess you can get used OE ones for a bit less too now?

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Mac
2002 e320 4matic estate│1985 300d│1980 300td
Previous: 1979 & 1982 & 1983 300sd │ 1982 240d

“Let's take a drive into the middle of nowhere with a packet of Marlboro lights and talk about our lives.” ― Joseph Heller, Catch-22