My Lada Vesta's left parking lights keep burning out even though I put in new ones. The right side works fine. I see a green coating on the connector - looks like oxidation. Do I need to take apart all the wiring in the trunk or is it enough to just clean the contacts?
No need to rip apart the entire trunk - that's a common mistake. If you can already see green buildup on the connector, there's a pretty good chance that's exactly where the problem is. Oxidized contacts create poor connection, which is why the light either glows dimly and burns out quickly, or doesn't work at all. Start with the simplest thing: disconnect the negative terminal on the battery, pull the connector out of the clearance light socket and look at it carefully.
Clean the contacts with a toothbrush and a bit of alcohol or WD-40 - literally just a couple of strokes. If the contacts are in really bad shape, it's better to just replace the connector altogether, they're super cheap. Also check that the bulb fits snugly in the socket, and examine the bulb itself carefully - the filament might already be darkened. After cleaning or replacing the connector, screw in a new bulb, reconnect the battery and check the clearance lights. If they keep burning out again, then check the wire, but in 90% of cases cleaning the oxidized contacts does the trick.
Green buildup on the connector is copper oxidation, and it almost always creates poor contact and burns out the bulbs! First try the simplest method: disconnect the connector, wipe the contacts with regular sandpaper (even the finest grit) or an eraser to remove all the buildup until it shines, then plug it back in.
If that doesn't help, then check the wire - it's possible that somewhere along the way from the connector to the headlight it's damaged or getting damp in the trunk.
But nine times out of ten it's the contact cleaning that does the trick, so start with that!
First, try starting with the connector, because the odds are about 90% it's the problem. Disconnect it and look more carefully - the green coating can be not just on the outside, but on the actual contacts inside too. If the coating is just surface-level, regular sandpaper will work fine (fine grit, like 120-150) or even an eraser. Polish the contacts until they shine, blow off the dust.
After cleaning, treat the contacts with a protective compound - WD-40 or special contact grease (you can find it at auto shops) will do. This will prevent oxidation from happening again. You'll notice the difference right away: if the lamp was flickering or working poorly before, it should light up properly after treatment.
If the lamp still burns out after cleaning the connector - then yeah, go ahead and check the wiring further down. But in 95% of cases like this, just getting the contacts in shape is enough.
Contact grease or WD-40 - that's what'll save you here. I used to struggle with stuff like this on my car too, until I figured out that connector oxidation is fixed with chemistry, not mechanics. Just disconnect the connector, apply some grease or spray WD-40, let it soak for a couple minutes, wipe it off with a rag and plug it back in. The main thing is make sure the contacts are completely fine and fit snugly into the socket.
One thing to add though - if you're gonna clean it with sandpaper, then definitely treat it with a protective coating after, or it'll just oxidize again in a month or two. That happened to me - cleaned everything properly, then August rolled around with higher humidity - green corrosion again. Now I either coat it with paste or just use alcohol + protective spray. And yeah, check the bulb itself - if it keeps blowing when there's poor contact, the voltage spikes and it burns out faster.
You don't actually need to tear apart the whole trunk. It all comes down to this connector.
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