headlight – Airheads Beemer Club

Headlight modulators

Headlight modulators are, or can be controversial, with differing viewpoints & arguments for & against. Some find modulators annoying. I believe that is, perhaps not always, folks seeing OTHER folks’ modulators, not their own. Some are concerned about oncoming drivers fixating on one’s modulating headlight & aiming for them, this seems to come from the idea that a motorcyclist tends to ride to wherever they fixate on. Studies have shown that adding lights at the rear (& in some instances the sides) of motorcycles makes them more visible and recognized earlier. For the rear, the lights should be red & as differentiated as possible between Run & Brake. Bright clothing, greenish-yellowish helmets, etc. …all have been shown to reduce accidents. I see no one arguing about ‘fixating’ on THEM.

Whether or not to install a headlight modulator on YOUR bike, is a personal choice; the USA government has not made them mandatory. My comments in this article apply to the USA, as headlight modulators may not be legal in some other Countries.

There ARE reasons that motorcycles are specified, since 1978 in California, & specified in many other States, to automatically, upon ignition turn-on, to power headlights ON, without having to manually turn the headlight(s) on. State law & Federal law are not necessarily the same thing, but, typically, Federal law supersedes. In this instance, always on headlights after a certain year model does apply. There is also an argument about certain cars, such as late models, having constant-on headlights …the argument usually is negative, as motorcyclists want only themselves to have such lights, to differentiate between them and cars. That’s a decent argument, but tends to favor modulators in use during the daytime.

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Accessing the Headlight Bucket

The fairing-equipped Airheads began with the 1977 R100RS. The headlight bucket is basically the same as in the unfaired models (except for later models not having fuses, etc., in the bucket). The bucket is not part of the fairing. On the RS and RT the bucket is located behind the front-most protective glass that is part of a ‘tunnel’ assembly with a large protective rubber molding with an outer glass, etc., whose design is such that it offers a relatively smooth front surface to oncoming wind, etc. The expensive outer glass has some orange lines on it. There is no purpose to those lines (stories abound, all wrong) except to draw the eye away from the quite large front glass. While the orange lines were purposely installed for that stylish effect, the headlight/bucket was quite far inwards from the front of the fairing, and thus the outer fairing tunnel glass needed to be of substantial size to prevent narrowing of the headlight beam. There is no aiming or other purpose to the orange lines.

Don’t do any disassembly of the fairing beyond what is noted below, unless you have a good reason to do so!

1. Fold back, barely (just a small amount), one corner at a time, each corner of the rubberized material surrounding the $$$ glass in the fairing. That will just barely expose a phillips screw at each corner.

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Headlight Switches & Headlight Relays

This article was originally written (and since then, expanded/edited numerous times) because someone asked about the left-hand switch of BMW Airhead motorcycles if using higher powered headlight bulbs. He did not understand why the existing stock headlight relay would not automatically eliminate wear on the switchgear. The simplified reason is that the stock headlight relay does not do what many think it does, at least on most, especially later, Airhead models. Variances of his question have come up many times, often on the Airheads LIST, but also on various other forums, and even for other BMW models.

It is important to know that the main purpose of the stock headlight relay FROM 1978 is to turn off the headlight, leaving the dash lights and rear running lamp on, during the time the starter motor is cranking the engine. The relay turns off the headlight during cranking, and that’s all.The stock headlight relay from 1978 also does not do theswitching between high & low beams. NOTE that the high beam flasher (‘passing lamp’) function remains, due to a green wire from the ignition switch, as a separate circuit. The headlight relay may or may not turn off the headlight, during engine cranking, depending on year, model, & country shipped-to. On some Airheads, the high beam flasher button (‘passing lamp’ function) MAY be available with the ignition off. It is a matter of where the green-colored wire goes to. It is easy to move a green wire at the ignition switch, and thereby have the ignition be ON, but the headlight OFF, in the PARK function, but there is more to this, and this is not the point of this article.

Using additional relays to control higher-powered headlamps (stock is 55/60 watt) is a must; although some have gotten away with not doing so for some time. Note that the left bars switch assembly is fairly expensive. It is not designed to handle high-powered headlamps, and it would have been, …perhaps, …better if a relay had been used by BMW to handle all the current flow to the low and high beams. This is not difficult to accomplish, and such as the Eastern Beaver kit does it. With that kit installed (or, your own two relays), the bars light switch(s) would only pass current to the extra relay’s COILS. This means that using accessory relays will reduce wear on the left switchgear even with the stock headlight; and usually will increase light output slightly due to a more direct current path from the battery to the relay. This increases the headlight voltage to closer to battery voltage….another way of saying this is that a more direct power path reduces wire and some switching losses.

Sources for appropriate relays are any auto-parts store. However, www.EasternBeaver.com sells complete plug and play kits for your motorcycle, and they may even still have a version with a modulator if you wanted that.

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Headlamp Cutout Switch

This is simple and self-evident to most anybody with a soldering iron but here we go….

First a primer on headlamps. Rated at 55 watts, an H4 lowbeam headlamp consumes around 55 watts, I guess, which is something like 4-5 amps. With a 240 watt alternator and with barely any charge below 2500 rpm, goofing around in the city, prior to cranking on a cold morning, or when your electric system is failing, it would be good to be able to switch off the lamp. Moreover, the parking lamp is on all the time and can make-do for a substantial part of the safety and regulatory issues, especially in the daytime. Finally, if you need some lamp action, you can always flick on the highbeam the two habitual ways which are unaffected by this mod.

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