This Stupid Headlight Switch Circuit Board Is Setting BMW E46s on Fire

The BMW E46, the 3 Series of the ’00s, is a great driving platform with a healthy aftermarket that can still be bought and built with relatively modest means. They’re important cars to the culture, and we should be protecting them. That includes making sure the circuit boards behind their headlight switches don’t spontaneously combust. Yep. “LCM fires” have been discussed on BMW forums and Facebook groups for years, but somebody finally took the time to articulate and show exactly how they happen. And more importantly, how to prevent them.

Most of the issues that E46 owners deal with these days are standard old-car ailments like oil leaks and bad bushings. But there are a few platform-specific problems I see come up in owner groups with some regularity. Plastic cooling components like to fail and cause overheating, cracks can appear around the rear subframe mounts weakening chassis integrity, and the headlight switch can catch fire, even when the car’s not running.

Well, it’s not the headlight switch exactly—it’s the horizontal circuit board behind the switch known as the Light Control Module (LCM). In the left-hand-drive E46s most of us are familiar with, it’s located left of the steering wheel above the driver’s knee. And while there are a few different types of light switches in these cars (some have an auto setting, some have a fog light button), they all have the same basic construction.

I haven’t been able to pin down a hard number of how many E46s have actually been car-b-qued by an LCM fire or confirm if there’s any specific trim level more susceptible than others. But after watching Tyler O’Leary’s video on his YouTube channel O’LearysGenuineBMW, I don’t think any E46 variant (hardtop or convertible, with or without sunroof, automatic headlight mode or not) is completely safe from this potential issue. This clip should be required viewing for anybody who owns an E46, is thinking of buying one, or even just has a casual interest in the car.

There’s some speculation among owners online about clogged sunroof drains or leaving the lights in automatic mode being the culprit of these fires. But the fact is that E46s are pretty much all old enough to buy beer, so even cars without a sunroof could have moisture sneaking into the cockpit through old seals.

The problem, as O’Leary explains and shows us, is that these LCM circuit boards are getting constant voltage (that’s how you can turn the lights on even without the key in the ignition). When moisture gets to them, it causes corrosion. Corrosion creates electrical resistance. Resistance creates heat. Heat can become fire. Fire bad.

Interestingly, I’ve never been able to find a report of an LCM fire happening while a car was running and driving. I don’t know what to make of that, but you better believe I’m going to start checking the LCM on my wife’s 2003 BMW 330ci with some regularity.

If you have an E46, keeping your sunroof drains clear and making sure your cabin weather seals are nice is step one in LCM fire prevention. But given the prevalence of this issue, keeping an eye on the module itself is a smart idea. The inspection process O’Leary shows us is pretty simple—the hardest part is probably going to be popping off the trim around the light switch without cracking it.

Once you’ve removed the module, you’ll either see that you’ve got a clean one (nice) or a cruddy one (a bummer, but far better to find it now than when your dash is ash). You have some options once you gain access to the circuit board. You could try to seal it with some kind of moisture preventative, but use extreme caution and do some research first, so you don’t accidentally fry things with an incompatible chemical or something. You could also apply some silicone sealant around the exterior of the switch housing, but again, double-check your work and make sure you’re not creating unintentional material contacts.

You could replace your LCM entirely—you can use RealOEM to look up the part numbers—but they’re not cheap. FCP Euro wants almost $500 for the headlight switch my wife’s car has. There are plenty of used ones on eBay and in junkyards for far less, but you’d be rolling the dice again unless the seller takes the switch apart and shows you the LCM.

If you’re paranoid enough to be nervous about this but too lazy to actually investigate, I guess you could pull the battery from your car, cutting power to the LCM and everything else. But that’s no long-term solution unless you’re really planning to mothball your Bimmer for some reason.

Or, I guess if you actually hate your E46, rinse that LCM in your sink, re-install, park the car far away from your house, and get ready to collect your insurance check. Kidding! Kidding. Come on, guys.

Jokes aside, there is one more thing to be aware of as an owner facing this issue. The E46 LCM is looped in with the gauge cluster and associated with your VIN, so you will probably need to have a new light switch re-coded to work, and installing one may trigger what’s known as the “tamper dot.” That’s just a little tiny light that shows up near the odometer indicating the mileage may be incorrect—might not matter on a 10-owner 325i, but if you have a nice clean car, you’re not going to want that.

Luckily, BMW coding software called NCS Expert can be used to make a new light switch work properly, and another program called PA Soft can be used to clear the odometer tamper dot. I’ll let you look into those yourself if you’re serious about wanting to use them. There may be other coding methods, programs, and coding services out there as well, and of course, you can always call a BMW specialist shop to farm the work out entirely.

To those E46 owners who have been blissfully ignorant of this potential fire hazard and now have a new fear unlocked, I’m sorry. But I do hope this post and O’Leary’s video can help prevent some E46s from immolating. Despite their flaws, these really are exceptional cars that punch above their weight in terms of quality and driving dynamics. Even a stock, non-M E46 is a joy to drive when it’s running right and properly maintained. You’ve just got to treat them with respect as they enter their elder years.

Have you had to deal with any LCM-related issues on an E46 Bimmer? Tell me about it! My email’s andrew.collins@thedrive.com,

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