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post #1 of 24 (permalink) Old Dec 16th, 2009, 8:53 pm Thread Starter
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Headlight wiring

The poor engineering for the headlight ground on my 03K1200GT bit me in the ass last night, so today I removed the headlight assembly to see just how bad it was.

The ground wire coming from the external plug has been spliced in the past, apparently with a fresh piece of the same inadequate size wire and a new female connector which is obviously for a larger wire and terminal. Apparently whoever repaired it before, hoped the larger connector would resist overheating better. What they didn't plan on was, it loosened up and allowed surface corrosion to interfere with current flow and cause another heat related early failure.

With my background in electrical/electronic repair, fixing it right should be fairly easy, except for one thing. The idiot glued the damn lens on the assembly, so for now I just squeezed the larger female connector down to give it a really tight grip on the ground strip and cleaned up the ground strip terminals, then swapped the common ground wire to the easier-to-reach terminal, so I could reclean it from time to time, more conveniently.

I despise working on something someone else has already screwed up.

So now I'm considering solutions that allow me to retain the wiring and connections already inside the assembly. Obviously reducing the total current flow would help the situation considerably.

option 1) Stop using the high beam during daylight riding. This may be enough to prevent future failures, as long as I clean the ground strip terminals and squeeze the oversized connector back down again a couple times a year.

option 2) Add a 12V relay to shut off the low beam, whenever the high beam is turned on. This would probably be just fine for using the high beam during the day, but without the low beam to provide a wider light, riding in the country at night with just the high beam on may not be adequate.

option 3) Add a switch instead of a relay, to the low beam circuit. Then I could still have the low beam for lighting width at night in the country, even when using the high beam. This would again leave me cleaning the terminals and squeezing the oversized connector from time to time and just hoping it would be enough to keep it working.

option 4) Replace both the 55W bulbs with 35W HIDs. Reducing total current by more than 3 amps would seem to be a good idea, as long as the ballasts could be mounted outside the headlight assembly and utilise the wiring inside the assembly, just as it is. Does anyone know what voltage the HID bulbs actually operate on?

option 5) Use option 1 until I can take the time and trouble to cut the lens free, then rewire the assembly to a more reliable design. This does not preclude the subsequent use of option 4, although it will give me the opportunity to install the ballasts inside the headlight assembly, if that is the normal location for them.

...anything I overlooked? ...comments?

regards,
Joe
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post #2 of 24 (permalink) Old Dec 16th, 2009, 9:17 pm
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Leave the high-beam as-is. HID and flashing don't mix. Takes the bulb too long to get to a decent brightness for that. 35w HID for the low beam would help reduce the ground-side current. Instead of crimping, see if you can't solder the ground wire to the connector. More expensive, better connector.
Running a relay controlled by the beam switch and then using a larger wire gauge, say from the battery to the line side of the relay, then the same wire gauge from the load side of the relay to the bulb connector will make is slightly messier to change the bulb (if you don't go the HID route) but will give you better light on both low and high beam bulbs because the larger wire gauge doesn't have the voltage drop the existing wire does. Maybe ½ volt, but it makes a difference with both brilliance and bulb life.

I installed a 55w HID low-beam on the bike. Since I had to cut a hole in the back cover to run the wires from the ballast to the bulb, I added a ground wire so now each beam has it's own ground wire. Haven't had to run anywhere yet where I can use the high beam for any distance, though.



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post #3 of 24 (permalink) Old Dec 16th, 2009, 9:30 pm
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I don't think you can take the lens apart from the housing, factory glued by BMW.... well maybe with a Dremel. I looked at mine and that's the way I figured it is built, nothing in there had been touched by anyone else than the assembly line.... And BTW that is a very expensive headlight, you might want some sort of rock protection over it.

I've already done your option 3, switch for the low beam, but mostly to conserve the battery in case it weakens out, I learned that lesson on my GS.....and the little parking bulb stays on all the time and is enough to probably fool the cops if you live in an area with the "Headlight On Always" law. And probably easy also to find a brighter parking bulb to do that(Fool them...)

HID is the way to go, from other posts I have seen,the 35W is plenty of light, I'm ordering some for my bike and my car, too much wildlife at night up here!

Do you also get this dimming of the headlight when you hit the brakes at night....it is so annoying, and distracting.....also caused by wimpy wiring. My K100RS did that a bit but way worse on the K1200RS. I was thinking to go straight to the battery with a relay just to alleviate that and insure a more constant voltage to the HID ballast.

I've already added an extra ground to the headlight, but did not do it right, sent it to the frame, should have brought a large wire from the battery and install a proper ground post in the front somewhere where I can ground any extra equipment I may buy. There has been other posts where the headlight grounds failed, good thing you are looking at them....

Benelli 50cc at 14
Yamaha RD 200 at 16
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Honda CB 750 F at 18
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Last edited by h96669; Dec 16th, 2009 at 10:07 pm.
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post #4 of 24 (permalink) Old Dec 17th, 2009, 4:03 am
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The most common issue on motorcycles and cars is skimpy wiring which causes voltage drops on the high load circuits like headlamps, horn, rear stop and tail. That's why you get the light dimming and once they wrap the wire in the loom, you have to consider adding a decent 12 gauge wire externally. BMW must use a computer to design their looms for minimum copper content because they have so many connection points, some inside the loom where you can't get to them.

I read a write up once where a guy was complaining about his poor headlights. With the motor running he measured the normal about 14.4 volts across the battery but 12.7 volts across the headlight lamp. With both lamps lit he was losing something like 15 watts just in the wire. Of course his headlamp bulbs lasted forever because a 12% reduction in lamp voltage is a lot less light.

The best option not in the list is to run a separate ground in 12 gauge from the battery negative up to the cockpit, tie the existing brown headlamp ground across to it and use that connection point for the headlamps. If you go HID a relay isn't needed, but it helps with the handlebar switch life if you want to do it. That halves voltage drop on the oem wiring and would be adequate for HID. If you want to go the next step, partiucularly with bigger tungsten headlight bulbs, that involves adding a 'must have' relay, looking at the hot wire route and beefing that up. But HID's is the way to go. Whatever you do, don't start making 'ground' connections to the bikes metalwork. In places up front, the electrical conduction on anything but the clutch housing is unreliable, some metalwork is painted and things can stop working when bike frame parts are removed.

When you buy the aftermarket so called 'brighter' lamps, they just assume there are these kind of wiring losses and de-rate their lamp voltage so they overrun by up to 10% and of course don't last very long. Even less life if you thicken up the wiring.



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Last edited by voxmagna; Dec 17th, 2009 at 4:12 am.
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post #5 of 24 (permalink) Old Dec 17th, 2009, 7:39 am Thread Starter
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Never having played around with HID, I hadn't considered the startup characteristics. Thanks for pointing that out.

Unless the joint will be subjected to excessive heat, soldering is always my preferred method, but most professionals are far less skilled at soldering than I am. Crimping a connector is okay for signal wires, but not any connection that has to carry more than 1 or 2 amps. A swaged connection is just as good as a properly soldered connection and is much easier to get right, for people who have no training in high reliability soldering techniques.

regards,
Joe

Quote:
Originally Posted by Razel
Leave the high-beam as-is. HID and flashing don't mix. Takes the bulb too long to get to a decent brightness for that. 35w HID for the low beam would help reduce the ground-side current. Instead of crimping, see if you can't solder the ground wire to the connector. More expensive, better connector.
Running a relay controlled by the beam switch and then using a larger wire gauge, say from the battery to the line side of the relay, then the same wire gauge from the load side of the relay to the bulb connector will make is slightly messier to change the bulb (if you don't go the HID route) but will give you better light on both low and high beam bulbs because the larger wire gauge doesn't have the voltage drop the existing wire does. Maybe ½ volt, but it makes a difference with both brilliance and bulb life.

I installed a 55w HID low-beam on the bike. Since I had to cut a hole in the back cover to run the wires from the ballast to the bulb, I added a ground wire so now each beam has it's own ground wire. Haven't had to run anywhere yet where I can use the high beam for any distance, though.
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post #6 of 24 (permalink) Old Dec 17th, 2009, 8:10 am Thread Starter
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There appeared to be a thin rubber gasket, with some kind of sealing compound (permatex, RTV... whatever) that had also been added. I expect a hot knife will work just fine to cut it free without doing the kind of damage a dremel bit would do.

You know, in 45 years of driving and riding, I've never had a headlight broken on any kind of vehicle. Not even on the street legal dirt bike I abandoned wrapped around a tree back in the 70's :-)

The dimming of the headlight when using the brakes, is something that I only see if I use the front brake. The BOOST/ABS is malfunctioning on this bike anytime I use the front brake and the extra load from that over-active system does cause a noticable voltage drop. It doesn't happen when I just use the rear brake. However, I did notice the first time I rode this bike, when I used the kill switch to shut off the engine while the ignition was still on, the obvious dimming of the headlight clearly indicated an electrical problem. I was just hoping it would keep working long enough for me to get the ABS problem solved first.

regards,
Joe

Quote:
Originally Posted by h96669
I don't think you can take the lens apart from the housing, factory glued by BMW.... well maybe with a Dremel. I looked at mine and that's the way I figured it is built, nothing in there had been touched by anyone else than the assembly line.... And BTW that is a very expensive headlight, you might want some sort of rock protection over it.

I've already done your option 3, switch for the low beam, but mostly to conserve the battery in case it weakens out, I learned that lesson on my GS.....and the little parking bulb stays on all the time and is enough to probably fool the cops if you live in an area with the "Headlight On Always" law. And probably easy also to find a brighter parking bulb to do that(Fool them...)

HID is the way to go, from other posts I have seen,the 35W is plenty of light, I'm ordering some for my bike and my car, too much wildlife at night up here!

Do you also get this dimming of the headlight when you hit the brakes at night....it is so annoying, and distracting.....also caused by wimpy wiring. My K100RS did that a bit but way worse on the K1200RS. I was thinking to go straight to the battery with a relay just to alleviate that and insure a more constant voltage to the HID ballast.

I've already added an extra ground to the headlight, but did not do it right, sent it to the frame, should have brought a large wire from the battery and install a proper ground post in the front somewhere where I can ground any extra equipment I may buy. There has been other posts where the headlight grounds failed, good thing you are looking at them....
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post #7 of 24 (permalink) Old Dec 17th, 2009, 9:44 am Thread Starter
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This problem is not limited to vehicles. I've had to rewire low voltage power systems on ships and at remote locations such as navigation beacons and communication relays also. It's pretty common with all commercially produced low voltage power system wiring. In my experience, most battery power systems and backup power systems are inadequately wired for long term reliability.

Your example of 14.4 volts being dropped to 12.7 volts, is actually fairly typical and is perfectly acceptable to most manufacturers. The problem is, they don't bother to take into account the characteristics of bulb filaments when the charging system is overloaded or shut down. Bulb filaments are rated by wattage because they operate at such a high temperature that they draw reduced current when operating normally. A lower voltage will actually cause the current to increase. In your example, if the engine is idling, providing reduced charging current so that the electrical load exceeds the voltage regulator's output current, the battery terminals will drop to 12.6 volts. That results in the headlight voltage dropping to 10.9 volts, causing the two 55 watt bulbs to try to draw a total of 10.1 amps instead of the expected 8.7 amps. Typically, bulbs designed for 12.6 volts will draw increased current all the way down to 10 volts, before starting to draw less current. That means the headlight ground wiring has to be able to handle at least 11 amps for a pair of 55 watt bulbs. While fire prevention tables call for 346 circular mils per amp (AWG16), for wiring exposed to weather and vibration AWG14 would provide better long term reliability.

Installation of HID adds another design factor. While bulb filaments just draw more current with slight voltage reductions, electronic circuits are much more unstable and can stop working or even be destroyed by voltage drops that bulbs can handle. The addition of an electronic module (ballast) requires that the wiring be upgraded to allow less voltage drop as the bulb curent increases. Most designs consider that a 1 volt total drop in the wiring is acceptable, with half that being dropped in the connectors and the wire size being calculated to drop the other .5 volts. Personally, I have found that increasing the wiring size to allow only .25 volts being dropped in the wire at peak load, gives much better long term results. Assuming that we are still specifying two 55 watt bulbs, with one of them being HID, and half of the wire voltage drop is in the positive wires and the other half, .125 volts, is in the ground wire, the common ground wire would need to have less than .011 ohms of resistance. This specifies a minimum wire size of AWG14 for a ground wire up to 4 feet in length and AWG12 for a ground wire longer than 4 feet but less than 6.5 feet long. Of course, this does not include any calculations for inrush current that the ballast may require, since I don't know what that current may be.

regards,
Joe

Quote:
Originally Posted by voxmagna
The most common issue on motorcycles and cars is skimpy wiring which causes voltage drops on the high load circuits like headlamps, horn, rear stop and tail. That's why you get the light dimming and once they wrap the wire in the loom, you have to consider adding a decent 12 gauge wire externally. BMW must use a computer to design their looms for minimum copper content because they have so many connection points, some inside the loom where you can't get to them.

I read a write up once where a guy was complaining about his poor headlights. With the motor running he measured the normal about 14.4 volts across the battery but 12.7 volts across the headlight lamp. With both lamps lit he was losing something like 15 watts just in the wire. Of course his headlamp bulbs lasted forever because a 12% reduction in lamp voltage is a lot less light.

The best option not in the list is to run a separate ground in 12 gauge from the battery negative up to the cockpit, tie the existing brown headlamp ground across to it and use that connection point for the headlamps. If you go HID a relay isn't needed, but it helps with the handlebar switch life if you want to do it. That halves voltage drop on the oem wiring and would be adequate for HID. If you want to go the next step, partiucularly with bigger tungsten headlight bulbs, that involves adding a 'must have' relay, looking at the hot wire route and beefing that up. But HID's is the way to go. Whatever you do, don't start making 'ground' connections to the bikes metalwork. In places up front, the electrical conduction on anything but the clutch housing is unreliable, some metalwork is painted and things can stop working when bike frame parts are removed.

When you buy the aftermarket so called 'brighter' lamps, they just assume there are these kind of wiring losses and de-rate their lamp voltage so they overrun by up to 10% and of course don't last very long. Even less life if you thicken up the wiring.
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post #8 of 24 (permalink) Old Dec 17th, 2009, 10:50 am
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Quote:
Originally Posted by sloowpoke
This problem is not limited to vehicles. I've had to rewire low voltage power systems on ships and at remote locations such as navigation beacons and communication relays also. It's pretty common with all commercially produced low voltage power system wiring. In my experience, most battery power systems and backup power systems are inadequately wired for long term reliability.

Wanna come with us....we are heading up north to do beacons with a ship full of electrical problems......!

Benelli 50cc at 14
Yamaha RD 200 at 16
Yamaha RD 350 at 17
Honda CB 750 F at 18
Honda V45 Sabre at 24
BMW K100RS at 27
BMW R100GS at 34
BMW K1200RS at 53

Last edited by Razel; Dec 17th, 2009 at 4:47 pm. Reason: Fixed tags
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post #9 of 24 (permalink) Old Dec 17th, 2009, 1:14 pm Thread Starter
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While I do appreciate the offer of gainful employment in a field I am well experienced at, coupled with the joy of working on a ship that isn't dry, no thank you.

I like my landings to include lots of warm sunshine, tropical breezes and fresh coconuts. Failing in that, I require to take my bike aboard and be able to offload it to go for a ride occasionally and I know from experience that that won't happen, going north from BC this time of year.

regards,
Joe
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post #10 of 24 (permalink) Old Dec 17th, 2009, 1:39 pm Thread Starter
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I was thinking about the high beam socket and the spring clip/ground buss that holds it in place. That part is far too thin and springy to be copper, so it's probably copper clad steel. That would mean it also has more resistance than a copper buss. Cutting away metal to form the terminals that the ground wires connect to, means even higher resistance at the terminals. That would seem to be the probable reason that the common ground wire terminal is getting so hot. The wire itself is not getting hot on my bike, but the terminal is getting hot, melting into the plastic reflector and transferring heat through conduction, to the wire.

A little more thought has triggered some old memories.

When I was in Europe, back in the 70's, I couldn't help but notice that headlight in European cities is quite a bit different than American headlight use. The European low beam headlights were much dimmer than what I was used to. I seem to recall that they were 20 Watts or or less. Is it still that way today? If so, that steel clip should have been replaced with a part designed to handle higher headlight currents than are on the European market bikes. Is that the same part, regardless of which market the bikes are made for?

I'll have to look at that closer the next time I have it apart. It may be that the problem can be solved by simply taking that part out of the path of current flow.

regards,
Joe
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