Highbeam passing light works but lowbeams and highbeams don't

[jerko]

I found a similar post as this but the bike was a a R100 euro spec police bike so the wiring was a bit different.

I checked the headlight relay in the headlight housing and all the connections seem fine. I traced the wires as per the Clymers wiring diagram and everything seems to be right. Fuses are good and all the connections to the circuit board are solid. The horn switch works and the yellow switch, when in the middle position turns on the rear light. When in the top and bottom position, the rear light turns off and the only light the works is the highbeam flasher which is activated in the down position on the rocker switch. I checked continuity on the h4 halogen bulb and all 3 terminals are ok. I contact cleaned and WD-40'd the switches. I'm totally stumped.

 

[pglaves]

I found a similar post as this but the bike was a a R100 euro spec police bike so the wiring was a bit different.

I checked the headlight relay in the headlight housing and all the connections seem fine. I traced the wires as per the Clymers wiring diagram and everything seems to be right. Fuses are good and all the connections to the circuit board are solid. The horn switch works and the yellow switch, when in the middle position turns on the rear light. When in the top and bottom position, the rear light turns off and the only light the works is the highbeam flasher which is activated in the down position on the rocker switch. I checked continuity on the h4 halogen bulb and all 3 terminals are ok. I contact cleaned and WD-40'd the switches. I'm totally stumped.

Look for a headlight On-Off switch. If off neither high nor low will illuminate but flash still will.

 

[stevenrankin]

What bike?

What year, model is your bike? For /7 bikes after a certain year, the left handlebar switch had only the horn and high low switch. Headlights were always on and controlled by ignition switch for on park or off. There were some exceptions to the rules imported. For example my 78 RS, it is not a US specification bike but a European specification model. As such, it does not have the headlight on all the time system the US bikes have for that year. So, to help, year and model are needed.

I will wade in anyway, as I can be a bit of a know it all at times, LOL.

Do you have a three position light switch on the left handle bar? Horn button, and High low flash switch with a yellow headlight switch? If the "yellow" switch you are talking about is the headlight Off, parking, headlight on switch. There is a good chance it is corroded. I had this problem on my 78 R100RS.

There is not much holding the switch in place, a Philips screw in the back. Take it off the mount and try giving the guts a good shot of contact or electrical cleaner.

DO NOT try to take it apart to clean it further, unless you really like fiddling with tiny little springs and ball bearings. I have done this, only to watch the spring and ball bearing disappear over my shoulder after my fourth attempt to reassemble. The switch is so tempting to take apart, looks so easy Perhaps someone with better tools, motor skills and patience could disassemble clean and reassemble it without problems. I couldn't.

Unless, I have missed something, or I am talking about entirely different switch gear, It sounds like you have covered all the bases and the switch is the culprit. The bad news is, depending on the switch, if you can't get yours to work again, it is possible it is NLA for a new one. I ended up with one from a R90S, added wire to the ends to make it work on my RS. The other possibility is you might be able to just go with the still available always on version switch and with a bit of study on the wiring schematic, get the system to work. St.

 

[jerko]

Look for a headlight On-Off switch. If off neither high nor low will illuminate but flash still will.

There is a yellow switch with 3 positions. I toggled all the switches in each position and still nothing.

What year, model is your bike? For /7 bikes after a certain year, the left handlebar switch had only the horn and high low switch. Headlights were always on and controlled by ignition switch for on park or off. There were some exceptions to the rules imported. For example my 78 RS, it is not a US specification bike but a European specification model. As such, it does not have the headlight on all the time system the US bikes have for that year. So, to help, year and model are needed.

I will wade in anyway, as I can be a bit of a know it all at times, LOL.

Do you have a three position light switch on the left handle bar? Horn button, and High low flash switch with a yellow headlight switch? If the "yellow" switch you are talking about is the headlight Off, parking, headlight on switch. There is a good chance it is corroded. I had this problem on my 78 R100RS.

There is not much holding the switch in place, a Philips screw in the back. Take it off the mount and try giving the guts a good shot of contact or electrical cleaner.

DO NOT try to take it apart to clean it further, unless you really like fiddling with tiny little springs and ball bearings. I have done this, only to watch the spring and ball bearing disappear over my shoulder after my fourth attempt to reassemble. The switch is so tempting to take apart, looks so easy Perhaps someone with better tools, motor skills and patience could disassemble clean and reassemble it without problems. I couldn't.

Unless, I have missed something, or I am talking about entirely different switch gear, It sounds like you have covered all the bases and the switch is the culprit. The bad news is, depending on the switch, if you can't get yours to work again, it is possible it is NLA for a new one. I ended up with one from a R90S, added wire to the ends to make it work on my RS. The other possibility is you might be able to just go with the still available always on version switch and with a bit of study on the wiring schematic, get the system to work. St.

77 R100RS US. It has the exact controls you described. I did exactly as you mentioned and cleaned the inside of the switch. I wouldn't mind having the headlights on at all time since it is the law in Canada to have DRLs. I do have a switch for fog lights, hmm maybe I can hook it up to that. I need a quick fix as I have a safety inspection this week.

 

[20774]

You said you checked the light relay and the connections seemed fine. But is the relay functional? It appears from the diagram that the relay provides the ground to the headlights. The power for the high/low beam goes through the handlebar dip switch which ultimately gets input power from the bike's ignition switch. It sure seems like the light relay is in the middle of the whole thing.

 

[stevenrankin]

That would be my next guess

The simplest thing was to check the switch for corrosion. That done and everything hooked up and routed where it should be, the relay would be the thing to swap out.

As Kurt says, they are in the middle of things. St.

 

[guenner]

The light relay in the headlight compartment is energized with ignition on. It provides power to the headlight switch for low/high beam. The ground of the light relay goes to the starter relay and joins the connection to the starter solenoid. This provides ground through the coil of the solenoid until the starter button is pressed. Then solenoid is energized (12V) and now the 'ground' side of the light relay - connected to that solenoid wire - also gets 12V. Both sides of the light relay have 12V and hence the light relay falls off and the headlight turns off, no matter whether low or high.

The push button for the flash light is a separate switch. It gets its supply voltage straight from an ignition wire and therefore it is not controlled by the light relay. Also means that when you press this button while starting the motor the high beam stays on.

So, either the low/high switch is not working or, the light relay is not working.

First...
The light relay ($$$) on the ground side has a diode which might have burned out and hence the relay cannot be energized. You should hear the 'click' of the relay whenever ignition is turned on. Maybe do this with head light compartment open to better hear the 'click'.

No click...
If there is no 'click' then most likely the switch in the left combi assembly is either corroded or kaput. Maybe it can be disassembled and cleaned/repaired.

/Guenther

 

[stevenrankin]

All the time on Headlight

FYI Gunther, you are describing the typical Always on headlight system BMW adopted after a certain date due to US requirements. There are bikes, built before that (early /7 and late R90S bikes). which have a off, park and on switch on the handle bar along with the horn and hi lo flasher switch. I believe this is the system on Jerko's bike as it is a 77 RS.

He has checked all connections, the switch and all that is left to swap out is the relay. I do not see diodes in the ground wires of the head light system.

Relays do quit working, I have gone through three on my R80RT over the years and one on my 78 RS. I have never had a failed diode unless something drastic happened. (never on my bikes but in other electronic systems).

I do hope Jerko gets back to us with what he found and the fix. If it is a bad diode, I will eat crow and increase my knowledge. Cheers, St.

 

[guenner]

The diode I mentioned is "IN" the relay itself. This is a BMW specific relay and $$$. Before buying a new relay I would do the 'click' test I suggested for the relay.

I don't know whether a 1977 R100RS has a separate headlight ON/OFF switch so you can ride with the headlight off.

/Guenther

 

[jerko]

OK, so I tested the relay and all terminals get power from the supply at terminal 30. I do not however hear a clicking sound as I do with my starter and horn relay when I connect the the battery. Do I need to have the ignition switch on?

The bike starts so that means it has to be grounded since it is grounded via the starter relay which is connected to the solenoid wire as Guenther described right?

The connections on the relay are as follows:

87 2 grey wires -> one to the ignition switch and the other to 58u on the circuit board
87b yellow/white -> handlebar switch harness
30 2 reds -> one to the ignition switch and the other to circuit board which is connected to another wire to the starter relay
86 black -> starter relay
85 green/purple -> handlebar switch harness

Thanks for the help guys

 

[20774]

Maybe my Haynes is all wrong, but hardly anything matches to your description. Haynes doesn't even have a black wire going to the light relay. The red wires on terminal 30 seem OK. The other connections not so much.

I believe the way the relay works is: 12v power is applied across 86 and 85 (which should be ground). The relay should click. When it does click, you will get continuity between 30 and 87 as well as 30 and 87b. Without the power across 86 and 85, these connections should show open.

 

[jerko]

Maybe my Haynes is all wrong, but hardly anything matches to your description. Haynes doesn't even have a black wire going to the light relay. The red wires on terminal 30 seem OK. The other connections not so much.

Tell me about it. The electrical is sort of a mess. I'm probably gonna rewire the whole bike in the winter. I just need to have the headlight working for inspection this Friday so I can ride this summer

 

[20774]

Well, then, my Haynes shows:

87b -- grey wire going to fuse block pin 58
87 -- yellow/white to terminal 58 on the handlebar dip switch
85 -- brown ground to the headlight board terminal 31
86 -- green/gray to terminal 56 on the handlebar light switch
30 -- two red wires, one terminal 30 on the ignition switch, and one to terminal 30 on the headlight board which eventually goes to the starter relay terminal 87

 

[jerko]

Well, then, my Haynes shows:

87b -- grey wire going to fuse block pin 58
87 -- yellow/white to terminal 58 on the handlebar dip switch
85 -- brown ground to the headlight board terminal 31
86 -- green/gray to terminal 56 on the handlebar light switch
30 -- two red wires, one terminal 30 on the ignition switch, and one to terminal 30 on the headlight board which eventually goes to the starter relay terminal 87

Where do see the terminal numbers of the relays? I have both Haynes and Clymers and on the wiring diagram/legend doesn't show the specific terminals they are plugged into

 

[stevenrankin]

Ok

Okay, for the 1977 RS, There IS a switch on the left handle bar with the horn, high low and flash switch AND a three position switch with off, park and on. So to answer Gunther's question, yes, the 77RS, early model /7 bikes and the the last year for sure of the R90S COULD be ridden with the head light OFF. In 1978 or even late 77, the US government made it a rule bikes for the US market had to have the headlight on all the time when riding. The switch for those years until 81 or 82 had only the horn button and high low flash switch. In 81 or 82 BMW went to Japanese made switch gear and moved the turn signal switch from the right handlebar to the left. This was for US bikes only.

For the headlights to work, the ignition switch must be in the run position. The ignition switch has thee positions. OFF, parking light, run. For Jerko's bike the ignition switch must be in the run position and the left handlebar must be in the on position.

I know the relays are expensive after all BMW to me means Bite My Wallet, they do wear out.

Unless, the switch harness is traced back to the its terminus in the head light shell unplugged and the switch checked for continuity with a continuity meter, or, some way can be figured out how to check continuity of the switch, The Handle bar switch chan't be 100% ruled out as being bad. This is a lot of work and I am afraid beyond my scope as to how to write it up to do the task. Working in the headlight shell is a royal pain, and mistakes can be made when unplugging connections and plugging them back in.

For all the trouble involved with pulling the connections for the switch in the head light shell, I myself would just get a new relay and change that. if you have a friend with the same year bike, swap out the relay and see what happens. Mind you I don't just replace parts to get things to work. In this case, everything has been done and as I say, pulling the connections on the switch to check it for continuity is a bear. At this point of the game, I would have installed a new relay. If that didn't work, I would replace the switch. Problem now is, the switches are NLA from BMW. The only left handlebar switch available is the headlight always on switch for the 78 and newer bikes. I am not going to say anything about installing one of them. I would imagine it might be easier as there are less wires. That is another thread.
I know, I am long winded. I wish many times I could teleport or help someone in person. I have my lift and tools as well as an airhead shop nearby. Cheers. St.

 

[pglaves]

We still have NOT received an acknowledgement from the OP whether his bike has or does not have an on-off headlight switch which he has verified is in the on position. Unless I missed that in the fuzzy conversation.

 

[20774]

Where do see the terminal numbers of the relays? I have both Haynes and Clymers and on the wiring diagram/legend doesn't show the specific terminals they are plugged into

Not a great picture, but this site has a diagram and legend for the 1977 model:

https://www.powerboxer.de/schalt-wartungsplaene/110-schaltpl-foxer

You could bounce that off the 1978 picture:

http://www.omnilex.com/public/bmw78/78r100wire.jpg

 

[jerko]

We still have NOT received an acknowledgement from the OP whether his bike has or does not have an on-off headlight switch which he has verified is in the on position. Unless I missed that in the fuzzy conversation.

There is an on/off/parking switch and I've toggled between them all as well as the high/low beam switch with the ignition in the 'ON' position and still nothing. Will try replacing the relay as STEVENRANKIN suggested

 

[pglaves]

There is an on/off/parking switch and I've toggled between them all as well as the high/low beam switch with the ignition in the 'ON' position and still nothing. Will try replacing the relay as STEVENRANKIN suggested

Thank you. Have you tried cleaning this switch with electric cleaner?

 

[stevenrankin]

Yes

From what I have seen, this is a 77 RS.

The two schematics Kurt has given us show the three position switch on the left handle bar. The German monochrome schematic is pretty hard to read but the three position switch is shown for 77RS.

The color schematic is easier to read but, it is for a 78 bike. I see a note below the switch marked for UK only. Bingo, that is the same schematic as the 77RS Jerko has. I know this because I used the 77RS wiring diagram to figure out my headlight system on my 78 European specification bike. So, other than the US bikes in 78 not having this switch, European bikes did. For me, It worked out. I am going off track now.

Gunther, I take it you mean the diode you are talking about is IN the relay itself? I do not see a diode in the headlight system at all. Unless you are seeing one at terminal 85b on the board? That is the only diode I see if, the symbol is for a diode in the schematic I am looking at Kurt supplied. I am afraid I don't have my Clymer schematics or BMW schematics handy right now.

I must be strange, I have not found this thread to be fuzzy in the least. Albeit, there is some confusion about the switch arrangement. Perhaps I have gotten a trifle too wordy my apologies if so. I should have taken some pictures and posted them in regard to what I am talking about in relation to the positions of the ignition and the headlight switch. I can't do it tonight but if anyone thinks it will be helpful, I can do it tomorrow morning. Cheers for the night. St.