High Beams work; One light out on low beams
 

My 81-300SD has the driver's front headlight out on low beam, but works on high beam. The fuse is a little corroded, but not broken.

Is the bulb for high beams separate from the low beams (I know this may seem like a stupid question for some of you.)? I am trying to check this out and fix it in the pouring rain, so I can't see in the sealed unit if bulb is damaged.

Thanks for any help.

Don

Sounds like a bad bulb. Those are the sealed type right (non-halogen)? They're cheap enough that replacing both should be your first course of action, right after breaking out the multimeter to make sure they're getting current.

Yeah, replace both of 'em at the same time. Other wise your car will look squinty going down the road with one bright new light and one old one.

Plus its illegal to use high beams when it is not the correct time to do so.

Yes, it's a separate element in the sealed unit. You can verify that the lamp is faulty by swapping the left and right. If the problem moves, it's the lamp; if the problem stays put, it's the circuit.

Or you could just test for continuity on the bulb and check for current on the connector.

I wounldn't hesitat to change the fuses for the headlights as well since they are corroded.

My bet is that someone who would understand how to do that would not be asking basic questions about light bulbs.

Time for a new bulb!

Swap the bulbs, if the good one doesn't work on the other side, carefully pry the back off the connector and give the terminals a slight squeeze with plyers. It wouldn't hurt to hit the male ends with a bit of sand paper. These connectors are not weather packed and are prone to a bit of corrosion. That is was exact problem with my right lowbeam.

Don't forget adding a bit of dielectric grease when you reassemble will help to stop future issues with the corroding of conductors.

try replacing the fuse...seen it happens twice for exact same issues

dielectric grease can solve the oddest electrical problems, once I discovered it a few years ago I always keep some in my toolbox.

check alignment after replacing
 

Don't forget to check the headlight alignment after replacing the bulbs. Might have to adjust them a bit.

Some hints for buying replacements.. Take the old bulb in with you -- a lot of the books at the autoparts stores have the wrong bulbs listed these days for MBs that old. If it has the same number of filliments and the same connector on the back, and is the same round/rectangular shape (don't laugh.. that's what they got wrong), it should work. There's newer bulbs out there that have a higher wattage rating -- try not to go too much over the wattage of the one your replacing or you'll be blowing fuses all the time -- it should say on the old bulb, or use the rating on the lowest equivalant. Lastly, replace them in pairs so you don't end up with a bright one and a dim one.