81 300D electrical weirdness

I drive an '81 300D.
I was driving home from work one night recently and I quickly noticed that I was riding cyclops. The right low beam was out. I flicked the
turn signal stalk back, and both high beams came on.
I took this opportunity to replace both headlight units with new Sylvania H6024XV sealed beams.
When I got the replacement lights hooked up, I discovered that the right low beam would still not come on. Furthermore, I found that when I pulled the rotating switch outward, the fog lights no longer came on.
I'm not an expert on these or any other cars. I gave up after I found a little fuse box under the hood on the driver's side. All of the fuses appeared intact, although I must admit that I'd never before seen fuses that looked like these; I observed that none of the little metal strips were burnt or missing, and that everything was firmly seated.
Now it's vehicle inspection time, and I need to resolve this annoying issue.
I ask you: what's up with this crap? Does it sound like something simple, like a bad headlight switch? Or am I in for wiring hell?
I'd prefer to take the car to a professional rather than do further damage by attempting a complex electrical repair myself. I'd appreciate it if an experienced W123 person could tell me what kind of trouble I've got on my hands.
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German cars use silly unreliable fuses. Or they did. And never trust any fuse, in any car. Find the fuses involved in your problem and spin them with your finger, or replace them and clean their holders.
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These fuses may look okay. but once you take it out, you will see it is corroded at the contact spots or fall apart. Just put new fuses in. Change them all, they are cheap online.
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The quick solution is to "roll" the fuses, spinning them cleans the contact surfaces somewhat. The correct fix is to disconnect the battery, remove all fuses, clean the contacts gently with a brass brush (steel will embed steel particles making the problem worse) , give them a *very* light coating of silicon spray to prevent corrosion, then replace all fuses. At least on a Benz the fuse box is nearly sealed. Old VWs have them practically exposed to the weather, and on my Jetta Diesel they are under a common water leak around the windshield
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Stop panicing, this is easy to fix.
First change ALL the fuses and chean, with a pen/ink eraser all the fuse contacts.
That alone may fix it.
There are no relays on your car for headlights, so there's only wire and a connector between your battery and the headlight. Get a $10 voltmeter from Radio Shack (I assume you don't already have one or you'd have used it and found the problem by now). Check voltage at the fuse on both side, and at the connector.
Keep gong and find where the electrons stop. It's not the switch if it's only one side. My money is on the connector to the headlamp.
It won't hurt to douche them in rubbing alcohol and cleaning them up with a nail file or something.
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It wasn't the connector. It was just a fuse. I tried your eraser idea and replaced all the fuses with ones I bought at Olympus. The right low beam and fog lights work great now.
None of the fuses I removed look bad. I guess you really can't tell.
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