Author Topic: Headlight Relays  (Read 20791 times)

Offline frankenduck

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Headlight Relays
« on: May 02, 2011, 02:08:54 PM »
Lots of people add headlight relays to their K bikes. Why?

1) The stock wiring for BMW headlights is rather wimpy.  It suffices but given the small gauge of the wire, voltage is lost in the circuit.  By upgrading to thicker wire (like 14 gauge or even 12) the amount of voltage lost is much less.  More voltage to your headlight means more light.

2) Since, from the factory, the headlight does not use relays this means that all of the current travels through the contacts in the high beam/low beam switch on your left handlebar.  Every time you switch between beams a little spark is created.  Over time and many uses, these little sparks degrade the switch contacts and eventually cause the switch to fail.  When you use relays, the current flowing through the switch is reduced to next to nothing and this increases the longevity of your headlight switch.

3) Once you've upgraded the wiring and added relays you can switch to a higher power bulb.  If you tried that with the stock wiring chances are you'd melt the insulation off of the wires and have some potentially serious problems.  (I run a 90/100W Xenon H4 headlight bulb which is a massive improvment over the stock halogen H4 bulb.)

You have two options when adding headlight relays:

1) Buy a kit from Jim Davis at Eastern Beaver.  If you're not into chasing electrons or just don't feel like making your own, Jim's kits are handy, fairly priced and used by lots of K bike owners.

Jim's page of H4 headlight relays:
http://www.easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html

2) "Roll your own"

You can find a couple of write-ups on this over at the IBMWR K Bike Tech Pages:

http://www.ibmwr.org/ktech.shtml

You can  either use your existing headlight plug and cut the wires very close to the headlight socket or you can get a new H4 headlight socket and connect your higher gauge wiring to the socket. This is really the "right" way to do things. (I get mine from Jim Davis.)



I'd also recommend using Posi-Taps to tap into the headlight wires from your switch.  Jim Davis has those too.  You'll need two of the PT1800 type.  (I do not recommend using ScotchLocks or T-taps - both have a tendency to fail or cut through the wire you're tapping into.)

Here's a how to wire headlight relays. Note that the wires indicated by thicker lines are the ones where you should use 12 or 14 gauge wiring:
Once I had a Collie pup
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Offline frankenduck

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Re: Headlight Relays
« Reply #1 on: January 08, 2012, 06:39:31 AM »
By the way, on many K bikes you'll also notice a white nylon single wire connector in your relay box.  If this is connected then both your high and low beams will be powered when the high beam is on.  Once you've added relays it's probably a good idea to disconnect this as having both beams illuminated on high isn't really necessary.
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline Scott_

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Re: Headlight Relays
« Reply #2 on: January 08, 2012, 08:48:20 AM »
By the way, on many K bikes you'll also notice a white nylon single wire connector in your relay box.  If this is connected then both your high and low beams will be powered when the high beam is on......
When did they start doing this? :hmm:
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Offline frankenduck

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Re: Headlight Relays
« Reply #3 on: January 08, 2012, 01:32:57 PM »
By the way, on many K bikes you'll also notice a white nylon single wire connector in your relay box.  If this is connected then both your high and lows beams will be powered when the high beam is on......
When did they start doing this? :hmm:

I think it's only found on the earlier wiring harnesses on the 2V bikes.
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline Scott_

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Re: Headlight Relays
« Reply #4 on: January 08, 2012, 04:18:02 PM »
That explains why I haven't seen in on either of my bikes.....
Thanks.
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1997 K1100LT 0302488
1995 K1100LT 0302044
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Garmin Zumo 550
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Offline wmax351

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Re: Headlight Relays
« Reply #5 on: May 05, 2012, 03:53:58 AM »
By the way, on many K bikes you'll also notice a white nylon single wire connector in your relay box.  If this is connected then both your high and low beams will be powered when the high beam is on.  Once you've added relays it's probably a good idea to disconnect this as having both beams illuminated on high isn't really necessary.

Interesting... I just bought a 130/100 H/L bulb, so I probably don't want to have both on at the same time. Currently, my bike only does one on at a time.


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Offline mystic red

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Re: Headlight Relays
« Reply #6 on: May 05, 2012, 10:45:35 AM »
By the way, on many K bikes you'll also notice a white nylon single wire connector in your relay box.  If this is connected then both your high and low beams will be powered when the high beam is on.  Once you've added relays it's probably a good idea to disconnect this as having both beams illuminated on high isn't really necessary.

Interesting... I just bought a 130/100 H/L bulb, so I probably don't want to have both on at the same time. Currently, my bike only does one on at a time.

You'll light up the world with that baby. You'll love it.

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Offline wmax351

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Re: Headlight Relays
« Reply #7 on: May 05, 2012, 04:14:41 PM »
Quote
You'll light up the world with that baby. You'll love it.

Should work nicely. I like the selective yellow too: makes you stand out.


Got a pair of some cheapo, harbor freight fog lights I modified for inverted use. Stick those on with a couple of 55 watt h1 bulbs, and I am in business.
  • Ann Arbor, MI on the way to ABQ, NM
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Bikes:
Current:1991 BMW K75 Standard, 1998 Moto Guzzi California EV11
Past: '83 BMW R65LS, '75 Honda CB550F, '69 Honda CB175, 1999 Royal Enfield Bullet 500, 1973 Triumph Tiger TR7V, 1971 BMW R75/5 in Toaster outfit, 1979 Harley Davidson XLS-1000 Sportster Roadster

Offline mystic red

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Re: Headlight Relays
« Reply #8 on: May 05, 2012, 04:23:01 PM »
I've been running the       
CATZ H4 Gold iridium Ion Yellow All Weather bulb for a while. Like it. Low watt with high output. Seems to be as advertised but light output can be very subjective. :deal: :yes

Offline wmax351

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Re: Headlight Relays
« Reply #9 on: May 05, 2012, 06:39:03 PM »
I've been running the       
CATZ H4 Gold iridium Ion Yellow All Weather bulb for a while. Like it. Low watt with high output. Seems to be as advertised but light output can be very subjective. :deal: :yes


I usually prefer to just go with the high watt=high output bulbs. I have a 50 amp alternator for a reason :)
  • Ann Arbor, MI on the way to ABQ, NM
  • 1991 BMW K75 Standard, Refreshed '94 engine
Bikes:
Current:1991 BMW K75 Standard, 1998 Moto Guzzi California EV11
Past: '83 BMW R65LS, '75 Honda CB550F, '69 Honda CB175, 1999 Royal Enfield Bullet 500, 1973 Triumph Tiger TR7V, 1971 BMW R75/5 in Toaster outfit, 1979 Harley Davidson XLS-1000 Sportster Roadster

Offline mystic red

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Re: Headlight Relays
« Reply #10 on: May 05, 2012, 06:59:00 PM »
I had one of the 130's before this one and this is comparable. Only yellow. Now he needs to come out with a 130/100 with the output of a 160/130. I'd have to be all over that. :biggrin:

Offline wmax351

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Re: Headlight Relays
« Reply #11 on: May 05, 2012, 08:24:05 PM »
At a certain point, it makes more sense to just add additional lights. Redundancy, in addition to more light output, that can be better aimed.

I saw an alternator mod on ADVrider that had some aussie set up an R100gs with a belt driven car alternator to run aircraft landing lights. I think they are something like 200 watts each. 800 watts total.

http://www.advrider.com/forums/showthread.php?t=225223&highlight=alternator
  • Ann Arbor, MI on the way to ABQ, NM
  • 1991 BMW K75 Standard, Refreshed '94 engine
Bikes:
Current:1991 BMW K75 Standard, 1998 Moto Guzzi California EV11
Past: '83 BMW R65LS, '75 Honda CB550F, '69 Honda CB175, 1999 Royal Enfield Bullet 500, 1973 Triumph Tiger TR7V, 1971 BMW R75/5 in Toaster outfit, 1979 Harley Davidson XLS-1000 Sportster Roadster

Offline Snowy

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Re: Headlight Relays
« Reply #12 on: May 06, 2012, 05:25:06 AM »
On my K1100RS I use an Eastern Beaver relay with Philips Xtreme bulbs at the standard rating 55/60w. I have also fitted a pair of Hella FF50 spot lights mounted under the mirrors using a pair of mounts I got a couple of years ago from a member here. I made up a loom with relay, fuse etc and thats powered from the relay box. I find this set up really good and has built in redundancy. Its not as good as the set up I have on the GSA which uses the same spots but with 50w HID conversions fitted. As the standard lamp also has a 50w HID fitted, when I turn these on its like switching the sun on. Truly awesome lighting and since I ride a lot at night and have quite a few deer and other critters where I live its absolutely necessary to have good lights.
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Online billday

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Re: Headlight Relays
« Reply #13 on: December 30, 2012, 10:37:02 AM »


1) Buy a kit from Jim Davis at Eastern Beaver.  If you're not into chasing electrons or just don't feel like making your own, Jim's kits are handy, fairly priced and used by lots of K bike owners.

Jim's page of H4 headlight relays:
http://easternbeaver.com/Main/Products/H4_Kits/h4_kits.html


That URL has changed, here's a good one: http://www.easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html

(Busy poring over his pages, trying to figure out what's best for me to buy with my Xmas $$$...)
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Offline frankenduck

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Re: Headlight Relays
« Reply #14 on: December 30, 2012, 01:52:33 PM »
Thanks for the heads up. I updated the original post.
Once I had a Collie pup
Dug a hole and covered him up
Now I sit there by the hour
Waiting for a Collie-flower

Offline Shiny

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Re: Headlight Relays
« Reply #15 on: August 11, 2016, 06:23:27 AM »
That URL has changed, here's a good one: http://www.easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html

(Busy poring over his pages, trying to figure out what's best for me to buy with my Xmas $$$...)

I'm electrically hopeless, which kit would be best for my K75?
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Online Laitch

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Re: Headlight Relays
« Reply #16 on: August 11, 2016, 07:28:25 AM »
I'm electrically hopeless, which kit would be best for my K75?
It sounds right now like no kit would be best for your bike until you feel more hopeful. :giggles 
Even the basic H4 Single In Shell plug into old connector, fuse holder-battery connect model requires attention to detail regarding wrapping to prevent problems.
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Offline xpc316e

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Re: Headlight Relays
« Reply #17 on: August 25, 2016, 09:50:57 AM »
If you are going to fit relays and a high-wattage headlamp bulb, do not forget to fit a ceramic bulb holder. They cost very little, but high-wattage bulbs give out enough heat to melt a normal plastic holder.

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