BMW K bikes (Bricks)

You are not connected. Please login or register

View previous topic View next topic Go down  Message [Page 1 of 1]


jjefferies

jjefferies
Silver member
Silver member
(K75)   I've had a minor electrical fault with my headlight. It would intermittently turn off. A touch of the thumb to the switch or flashing it would correct the problem. Then this past week I noticed that they (high and low beams) were both off. Checked the bulb, it is fine. Flashing the high beam would still work. So I took the switch apart, an hour's work, cleaned off the contacts with 1500 grit paper, applied electrical lube spray, reassembled. Problem persisted. Called my bud, Greg, and he would sell me a used switch for USD$40. Ok, went over got it. 1st issue the connector was the wrong one. The connector on my K75 is a 3x3 grid. The one Greg had was 2x7. Ok back over and find a different left switch with proper connector. Bring it home and before tearing everything apart and installing it, connected it up and tested it. Same problem!! OK back to the schematics and what is going on? Can I have come across two switches with the same failure mode or is it something else? Just so you an identify the problem the headlight switch connector is under the tank on the left side and is housed in a somewhat soft plastic cylinder closed at the front and open at the rear. Also in the connector are the left turn signal and the horn switch leads. If you have a K75 then you will have undoubtedly noticed this connector as it is relatively large and different.

Three possibilities: is the problem in one side or the other of the connector, or in the switch? Description of circuitry. There are three wires involved, a power source, and a wire to each the low beam and the High beam. So elimination of possibilities, I found the power line on the harness side of the connector (green with Blue stripe) and the low beam (yellow) and the high beam(white). With bike power turned on Connecting the power line on the harness side in turn to the high and low beam produced light, i.e. the headlight lit up. Looking at the switch side with my Fluke 75 multi-meter I could not get continuity between the pwr(green w blue stripe) and either the low beam(yellow) or high beam(white) connectors with the headlight switch set in either low or high beam. I did get continuity between the power(green with blue strip)  and the high beam (white) if I pressed the switch as you would when flashing the high beam.

So at this point it would "appear" that two switches have failed in a similar if not the same manner. Has anyone else ever run into this particular failure mode and what was your resolution?

    

2Back to top Go down   An interesting K75 Electrical Gremlin Empty Gremlin Wed Jan 06, 2021 4:00 am

daveyson

daveyson
Life time member
Life time member
What hi and low have in common is a switch powered from the right handlebar connector through a white/yellow wire, except I think in the US,  where it's probably bridged. The flasher gets power from the green/blue wire at the left handlebar connector.

I'd look at the right hand connector, at the green/blue and white/yellow wires.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Arlina

Arlina
Moderator
Moderator
The 2x7 connector belongs to the K100/1100 16V models.

Many old switches are worn, if yours replaced bij another old switch, it could be worn also.


__________________________________________________
An interesting K75 Electrical Gremlin Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

Dai

Dai
Life time member
Life time member
I'm with Daveyson. Although the righthand switch may not have a light switch on it, internally the switch contacts should be bridged with wires.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
Yes, check the right hand switch wiring.  First thing I would do is clean the big connector under the tank.  That is probably all you need to do.

When you get it working again, get an Eastern Beaver headlight relay harness.  It's a fairly simple plug and play that bypasses the left hand switch with the high current being drawn by the headlight.

It's fairly inexpensive at about $60 shipped from Japan, and it will preserve your left hand combination switch as well as noticeably increasing the brightness of your headlight.  Every K bike I have owned has had one installed.  It's a great upgrade!


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

jjefferies

jjefferies
Silver member
Silver member
@daveyson wrote:What hi and low have in common is a switch powered from the right handlebar connector through a white/yellow wire, except I think in the US,  where it's probably bridged. The flasher gets power from the green/blue wire at the left handlebar connector.

I'd look at the right hand connector, at the green/blue and white/yellow wires.
When you say look at, do you mean at the connector which I assume is a connector similar to what I have described but lying on the right hand side of the bike? Or did you mean at the right handlebar? And what did you mean by in the US where it's probably bridged? I do note in the electric schematic (Clymer) that there is a "Lighting Switch (United Kingdom only)" which has leads Y/W, L/Gr, L/G. And I do see what might indicate a jumper between Y/W and LG. As well as one from Y/W and L/Gr. Sorry for being obtuse.

    

7Back to top Go down   An interesting K75 Electrical Gremlin Empty Gremlin Wed Jan 06, 2021 4:56 pm

daveyson

daveyson
Life time member
Life time member
When they say "UK only" I'm hearing "the rest of the world except the US" that's a guess.

Yep, as above, hopefully the big plug under the tank, right hand side, just needs a clean, and if you clean the left handlebar switch, read up on it first.

The Clymer manual is right except for the typos;
Y/W should be W/Y
L/Gr should be Gr/L
L/G should be G/L


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

robmack

robmack
Life time member
Life time member
Don't know if this helps or not.  The schematic below shows the two possible configurations for the right hand switch cluster.

An interesting K75 Electrical Gremlin Screen12

The dotted illustration on the left is the cluster complete with the Euro switch. Although it is labelled UK Only, I believe most European countries, and possibly most of the world markets for BMW, had these switch clusters installed.  For the US / Canadian markets, that switch was eliminated and the contacts were jumped.  You can see these in the same diagram as solid lines connecting Pins 4, 7 and 3.  This way, it was not possible to turn on and off the headlamp in these markets.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

jjefferies

jjefferies
Silver member
Silver member
@robmack wrote:Don't know if this helps or not.  The schematic below shows the two possible configurations for the right hand switch cluster.

An interesting K75 Electrical Gremlin Screen12

The dotted illustration on the left is the cluster complete with the Euro switch. Although it is labelled UK Only, I believe most European countries, and possibly most of the world markets for BMW, had these switch clusters installed.  For the US / Canadian markets, that switch was eliminated and the contacts were jumped.  You can see these in the same diagram as solid lines connecting Pins 4, 7 and 3.  This way, it was not possible to turn on and off the headlamp in these markets.
Hey thanks and an interesting lesson that it's the US and Canada that legislated that M/C headlights have to always be on.

    

Dai

Dai
Life time member
Life time member
@jjefferies wrote:
Hey thanks and an interesting lesson that it's the US and Canada that legislated that M/C headlights have to always be on.
Too many decades ago and I've lost my source by now. All I can recall is that it was a follow-up done by one of the brownstone unis.

- When initially legislated, motorcycle accident statistics went down. Hooray! This is working!
- A decade later they were higher than ever. WTF?? Must be those nasty dirty bikers doing something stupid. It always is.

Waallll.... turned out the cagies had got so used to seeing the headlights that they assumed the bike was further away than it actually was. So, seven years ago Europe went down the same route. Some time in the next three years or so I guess we'll start reaping the results of that, if we're not already doing so.


__________________________________________________
1983 K100 upgraded to K100RS spec, 1987 K100RT
Others...
1978 Moto Guzzi 850-T3, 1979 Moto Guzzi 850-T3 California,1993 Moto Guzzi 1100ie California
2020 Royal Enfield Bullet 500
    

11Back to top Go down   An interesting K75 Electrical Gremlin Empty Solution Thu Jan 07, 2021 9:58 pm

jjefferies

jjefferies
Silver member
Silver member
Thanks Daveyson, comments about the UK only on/off switch was the clue that got me looking at the schematics again. Still turned out it was the switch. According to another friend, Lee Fulton, it's not an uncommon problem. Particularly if you run a higher wattage bulb. But the little electrical contact buttons in the switch get hot and sort of melt back into the plastic reducing the contact and eventually causing the switch to fail. When I finally determined which leads were involved (white with yellow stripe(feed), white (hi beam), yellow (low beam), and measured the respective resistances the hi beam was 980 ohms and the low beam was infinite. So another switch is needed and then adding on one of the Eastern beaver relay systems will be the final solution.

Thanks guys.

    

12Back to top Go down   An interesting K75 Electrical Gremlin Empty Gremlin Thu Jan 07, 2021 10:49 pm

daveyson

daveyson
Life time member
Life time member
Good to see it was an easy fix. This reminds me I wanted to do the headlight relay upgrade too. It's probably because I rarely ride at night that it's near the bottom of my "to do" list


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

jjefferies

jjefferies
Silver member
Silver member
@daveyson wrote:Good to see it was an easy fix. This reminds me I wanted to do the headlight relay upgrade too. It's probably because I rarely ride at night that it's near the bottom of my "to do" list
I wouldn't say easy. Just straight forward. Did some shopping. The eastern beaver is a fairly expensive solution, approx USD $70. Though I do like the fact they use "Japanese" relays. Then I found this site: https://www.tomsbroncoparts.com/product/Heavy-Duty-Headlight-Wiring-Harness-66-77-ford-bronco-new?gclid=CjwKCAiA_9r_BRBZEiwAHZ_v15yE44v4u4vjhIOr5ct_ZHMEydJga1wwaD6JkMsQAKl4MLkmQM0AKBoCi74QAvD_BwE
Which does a somewhat similar solution for Bronco's but at USD $30. instead of $70. Being a president of the CABOA, I might lean toward this solution. Though considering how many relays I have in the garage, I might just check those out as well.

":""

    

Point-Seven-five

Point-Seven-five
Life time member
Life time member
@jjefferies wrote:
@daveyson wrote:I wouldn't say easy. Just straight forward. Did some shopping. The eastern beaver is a fairly expensive solution, approx USD $70. Though I do like the fact they use "Japanese" relays. Then I found this site: https://www.tomsbroncoparts.com/product/Heavy-Duty-Headlight-Wiring-Harness-66-77-ford-bronco-new?gclid=CjwKCAiA_9r_BRBZEiwAHZ_v15yE44v4u4vjhIOr5ct_ZHMEydJga1wwaD6JkMsQAKl4MLkmQM0AKBoCi74QAvD_BwE
Which does a somewhat similar solution for Bronco's but at USD $30. instead of $70. Being a president of the CABOA, I might lean toward this solution. Though considering how many relays I have in the garage, I might just check those out as well.

":""
The Eastern Beaver harness is a plug and play, the Bronco harness just looks like a bunch of parts that you will have to build a working harness from after cutting it all up.  If you have a bunch of relays already you might as well build a harness from scratch as use the Bronco harness.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

robmack

robmack
Life time member
Life time member
The Bronco harness is over-kill. It has one extra set of H4 connectors that will need to be eliminated or ignored. The wire lengths are probably very long and you'll have extra wire to hide. The schematic they provide is not detailed enough to determine if it will work properly so there is a risk right there. The Eastern Beaver harness is proven.

Your choice with the Bronco harness but make sure you can return it if it doesn't work out for you.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

16Back to top Go down   An interesting K75 Electrical Gremlin Empty Headlight problem Sun Jan 10, 2021 11:06 am

Kr4mo

Kr4mo
active member
active member
@robmack wrote:The Bronco harness is over-kill. It has one extra set of H4 connectors that will need to be eliminated or ignored.  The wire lengths are probably very long and you'll have extra wire to hide.  The schematic they provide is not detailed enough to determine if it will work properly so there is a risk right there.  The Eastern Beaver harness is proven.

Your choice with the Bronco harness but make sure you can return it if it doesn't work out for you.
Here's another option for the relays for the headlights.
https://culayer.com/product/matchbox-headlight-relay/

    

1990k75

1990k75
Silver member
Silver member
@jjefferies wrote:Thanks Daveyson, comments about the UK only on/off switch was the clue that got me looking at the schematics again. Still turned out it was the switch. According to another friend, Lee Fulton, it's not an uncommon problem. Particularly if you run a higher wattage bulb. But the little electrical contact buttons in the switch get hot and sort of melt back into the plastic reducing the contact and eventually causing the switch to fail. When I finally determined which leads were involved (white with yellow stripe(feed), white (hi beam), yellow (low beam), and measured the respective resistances the hi beam was 980 ohms and the low beam was infinite. So another switch is needed and then adding on one of the Eastern beaver relay systems will be the final solution.

Thanks guys.

What i see here is 'higher wattage bulb'. Anytime I add something which will draw more current than stock I add a relay. Contacts in handlebar switches are tiny & marginal at best for original loads, Relays are cheap.


__________________________________________________
Past bikes - Yamaha YL-1, Honda XL-125, 1967 BSA 650 Lightning

Current - 1990 K75RT (in drydock) & 1995 K75RT VIN # WB1056503S0372669
            - 2011 Suzuki V-Strom 650
            - 2011 Yamaha XT250

Who sez I'm too old to ride?
    

jjefferies

jjefferies
Silver member
Silver member
@1990k75 wrote:
What i see here is 'higher wattage bulb'. Anytime I add something which will draw more current than stock I add a relay. Contacts in handlebar switches are tiny & marginal at best for original loads, Relays are cheap.
I'd like to toss out two ideas that I'd appreciate your comments on:
1.) Use of an LED H4 headlight. Would that not also reduce the possible failure due to heating of the switch?
2.) How about use of some of the same type relays we have in the bucket under the tank? My count just now I have 23 of the various relays used on K bikes and that's not counting the ones in my parts bike. Yeah, I've had a few bikes and parts machines etc over the years. But surely a couple of those could be used as light relays. I've been of the opinion that they last for ever. Just thinking about repurposing rather than buying more.

I find it strange that I've never before encountered this problem of the headlight switch going bad due to heat. My Red K75 has 164,000 miles and no problem there. Though the same cannot be said of its heated hand grips. Left hand is too hot to hold and the right is freezing. That's my current project and will undoubtedly have it fixed in time for summer riding  Wink  Which BTW, brings up another subject for inquiry, bar end weights. I have them on Red and there always seems to be a problem with the right hand (throttle) side due to interaction between the power feed and the  mechanism for mounting the bar end weight. Any thoughts/comments on the usefulness of bar end weights and their fitting out with heated hand grips?

    

MartinW

MartinW
Life time member
Life time member
My fan cooled 40W LED globes spec sheet says it draws 1.6 amps which is too low. Doing the calculations it works out to 3.3 amps. A 100 W incandescent globe draws  8.3 amps.
Regards Martin.



Last edited by MartinW on Sun Jan 10, 2021 5:42 pm; edited 1 time in total


__________________________________________________
K75s Hybrid
    

robmack

robmack
Life time member
Life time member
@jjefferies wrote:Which BTW, brings up another subject for inquiry, bar end weights. I have them on Red and there always seems to be a problem with the right hand (throttle) side due to interaction between the power feed and the  mechanism for mounting the bar end weight. Any thoughts/comments on the usefulness of bar end weights and their fitting out with heated hand grips?
Read about how I handled the interference problem with aftermarket heaters : INSTALLING SYMTEC GRIP HEATERS ON K100RT++


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

1990k75

1990k75
Silver member
Silver member
@jjefferies wrote:
@1990k75 wrote:
What i see here is 'higher wattage bulb'. Anytime I add something which will draw more current than stock I add a relay. Contacts in handlebar switches are tiny & marginal at best for original loads, Relays are cheap.
I'd like to toss out two ideas that I'd appreciate your comments on:
1.) Use of an LED H4 headlight. Would that not also reduce the possible failure due to heating of the switch?
2.) How about use of some of the same type relays we have in the bucket under the tank? My count just now I have 23 of the various relays used on K bikes and that's not counting the ones in my parts bike. Yeah, I've had a few bikes and parts machines etc over the years. But surely a couple of those could be used as light relays. I've been of the opinion that they last for ever. Just thinking about repurposing rather than buying more.

I find it strange that I've never before encountered this problem of the headlight switch going bad due to heat. My Red K75 has 164,000 miles and no problem there. Though the same cannot be said of its heated hand grips. Left hand is too hot to hold and the right is freezing. That's my current project and will undoubtedly have it fixed in time for summer riding  Wink  Which BTW, brings up another subject for inquiry, bar end weights. I have them on Red and there always seems to be a problem with the right hand (throttle) side due to interaction between the power feed and the  mechanism for mounting the bar end weight. Any thoughts/comments on the usefulness of bar end weights and their fitting out with heated hand grips?

In my opinion (& Robmack knows way more than me) it's not 'heat' that causes switch failure, it's the amperage. For sure an LED option will draw way less current, but may complicate things because the LED 'bulbs' have heat problems - which is why they have heatsinks on them.
Bar end weights & heated grips problems are worthy of separate posts...


__________________________________________________
Past bikes - Yamaha YL-1, Honda XL-125, 1967 BSA 650 Lightning

Current - 1990 K75RT (in drydock) & 1995 K75RT VIN # WB1056503S0372669
            - 2011 Suzuki V-Strom 650
            - 2011 Yamaha XT250

Who sez I'm too old to ride?
    

22Back to top Go down   An interesting K75 Electrical Gremlin Empty Gremlin Sun Jan 10, 2021 7:38 pm

daveyson

daveyson
Life time member
Life time member
Yep you can use normal relays, I've got some that can accept fuses, making the job easier, but the kit would make it easier again.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

robmack

robmack
Life time member
Life time member
@1990k75 wrote:
In my opinion (& Robmack knows way more than me) it's not 'heat' that causes switch failure, it's the amperage. For sure an LED option will draw way less current, but may complicate things because the LED 'bulbs' have heat problems - which is why they have heatsinks on them.
Current does contribute to the problem of switch failure.  When a load (i.e. the headlamp) draws an amount of current from the power source, it encounters resistance across the switch contacts.  This resistance is inevitable because of corrosion buildup over time and because of the small contact patch between the wiper and the fixed contact.  Energy is lost across this junction in the form of heat.  Applying a load greater than the design limit for the switch contacts will cause failure. So, changing the H4 halogen bulb from 55W/60W to 60W/100W will exceed the design limit of the BMW OEM switch cluster and heat will melt the soft plastic used to retain the fixed contact.  The spring tension on the wiper pushes the now unsupported contact further into the plastic.  Result is a broken switch.

LEDs used in H4 LED bulb replacements are very efficient converter of electrical energy into light energy. So, relative to the current they draw from the power supply, LEDs output a great deal of light.  So bulb designers can reduce the current needs of a LED bulb and still get the designed light intensity.  But energy loss is inevitable.  If the LED chips in the bulb didn't have a way to shed that heat generated through lost energy, they would burn out almost instantly.  So the chips are bonded to a heatsink assembly that carries the heat away from the chip substrate.  That's why these bulbs have large heatsinks and sometimes tiny fans; to ensure good heat dissipation.


__________________________________________________
Robert
1987 K75 @k75retro.blogspot.ca
http://k75retro.blogspot.ca/
    

View previous topic View next topic Back to top  Message [Page 1 of 1]

Permissions in this forum:
You cannot reply to topics in this forum