R75/6 - problem with left-side switch, and/or headlight

Cool......thanks for the help HH

You DO NOT KNOW just how much I have read, and how many pages of writing AND drawing it has taken me to get to this point.

Now the next step.

I live in a small town so I am going to the NAPA to see if I can find an acceptable Relay.

Nearest BMW Dealer is 400 miles round trip.
I guess if I need to mail order one, I could do that too,
but off to town & the NAPA Store first.

will update after the next step is accomplished.

TheOldDustyOne

Yes ... if the relay is active AND there is 12 volts on 87b. (or is it 87a .. ?)

Relay is active if there is voltage across 85 to 86.

-------------
So you should have
0 volts on one relay pin
+12 on the other 3.

---------------
If you have only 2 pins with +12 and 0 on the other pins then relay faulty. (Humm this assumes some things... but is a 'useful indication'. Can be verified by checking the pin numbers to voltage readings.)

Warin, this Light Relay is a 5-pin relay,
and it appears to be the Standard OEM BMW Part.

30
85
86
87
87a

Max provides fast shipping (can be next day). Note that the part number has apparently be superseded.
http://www.maxbmwmotorcycles.com/fiche/DiagramsMain.aspx?vid=51887&rnd=04282014

click on "electrical system" (61) and scroll down to the "Lighting" diagram.

Here's a quote from the fiche:


61321358193 was superseded by 61321358198.
This is a headlight relay. Fits models 1974-1978.

Dusty, I feel your frustration. There are a couple of odd things going on here.

You mention that you think yours has the UK wiring. If this is the case your left handlebar switch should have a lighting switch in addition to the hi/lo switch (according to my Haynes wiring diagram). If this switch has been replaced with a US type switch I assume you will need to go with the US wiring.

Next, because the switched output from the relay is BEFORE the hi/lo switch on the handlebar the relay is not being used in the normal manner for a headlight relay.
It appears that the relay you have is the standard Bosch type 5 pin relay (pins labelled 30, 85, 86, 87 and 87a). This is the one marked as 'Changeover' in this diagram.



These are cheap and readily available. 30 is connected to 87 until the relay is triggered, when it is switched to 87a. But … this may be the incorrect type for BMW’s intended purpose.

The relay indicated in the Haynes wiring diagram has a pin marked 87b. Note the switching in the two 'headlight' relays in the above diagram. Both have double contacts, such that when triggered, 30 is connected to both 87 and 87b. (Don't ask me about the diodes - my knowledge of electrickery is limited). Dunno if your bike needs the diode version or not. One would need to figure out the logic of the circuit, and perhaps the notes under the picture of the diode-rich headlight relay in the above diagram will provide clues. I really don't know enough to assist here.

It may be that replacing the existing relay with the correct type (with the 87b pin) will fix the problem. If this is only available as an OEM part it's likely to be stupidly expensive. There may be other workarounds.

The other curious thing, looking at the Haynes diagram again, is that the relay trigger polarity is reversed for US/UK models. That is, for the UK model pin 85 is connected to earth (brown wire) and for the US model 85 is connected to a wire from the starter relay that is hot when the starter relay is energised. May be something to do with having lights on all the time and perhaps the starter relay connection.turns them off during starting.

I hope the above somehow helps rather than hinders your quest. Best of luck.

Hey Brun,
Thanks for the kind and helpful words......sometimes I think that I am just beating my forehead raw with this.

As to UK Wiring
........It looks like I ONLY HAVE PARTIAL UK Wiring in-place,
but that will need to be changed as I am going to wire in a different left-side switch from an 83 R100RT, as it was told to me.
At least I will be able to get away from that up&down right-side flasher switch.

No wonder the guy I bought it from waited to tell me about the lights
UNTIL AFTER I drove 250 miles to see the motorbike
He said that he only rode it daytime hours during the several months that he had it.....Now I see why.

So, here is the latest...AND LAST update for about a week:
I pulled the relay and took a close look at it
AND DEFINITELY it is an 87b
........not the 87a as the wiring charts led me to believe that was supposed to be there
(I had to use a magnifying glass AND a super bright flashlight in order to see those old worn-down German Terminal Numbers)
.....NO WONDER I was confused---AND with a BAD RELAY TOO!!
The 87b makes sense within all of this as it throws a DOUBLE OUTPUT SWITCH
(I also was driven to look at a number of wiring diagrams spanning several years of build dates----GEEZ, I am glad they ARE IN COLOR)

PLUS, it looks like there also has been some extra wiring modifications done to it......to what extent???
Not exactly sure at this time, so I am going to wait until I have a proper working relay in-place and powering the left-side switch.
(I have a cheaper used BMW-Car-Type 5-pin relay with the 87b terminal coming in the mail this weekend. I hope this will AT LEAST allow me to test out the circuits and go from there BEFORE I spend BIG $$$$$ on a specific relay for this)

Next update most likely will be next week AFTER I get that RELAY in and go from there
.....AND NO!!!.....You really do not want to see a pic of the wirings going every-which-direction inside of the little headlight shell

NOTE:
Once this is sorted out, I will even need to lay in FRONT TURN SIGNAL Wiring, but I do see just where those wires go

oaky now...short update:
This motorbike has, let me call it "a mix" of wiring, boards, relays, and switches :eek1

At this point, I AM making progress....and maybe I am close

HOWEVER.....I have just a couple of questions:
1.) What is the "supposed indication" of 56a on the circuit board when powered up by the key?

The reason I ask is this:
When key is on, and I put the tester to the 56a terminal, and I push the flash-to-pass, it lights up and stays on, as long as I hold down the flash-to-pass button.
HOWEVER
When I let go and then flip the button just to the high-beam position,
it immediately goes to -0- volts on the tester.
When done with the light tester, the indication is from nothing, then to a very quick bulb light up, then back to nothing.

The only other abnormal indication is that the horn NO LONGER works....it did work before when I started. And as far as I can tell, everything is hooked up fine.

EVERYTHING ELSE looks to be working just fine.
AND I now have a low beam since the NEW RELAY (87b-type) is hooked up.

COULD THESE 2 ISSUES be a blown fuse????

AND FUSES----where-o-where the fuses done-gone????:eek1

AGAIN as stated above....someone has changed/modified/ xxxxx the electrics, and this is MY 1st PROJECT on the motorbike.

THE ONLY PLACE I have yet to search is UNDER the fuel tank,
and I have no-idea of what I will find....other than fuses and a
front brake master cylinder

Dusty-
Your two 8 amp fuses SHOULD be located in your headlamp bucket, at the top of circuit board. They're not there? The horn notoriously blows a fuse. The fact that it's not working is a clue. Can't help with 56a at the moment...doing some auto maintenance before the next storm.

yeah....SHOULD is "the word of the day"
the circuit board I have IS NOT the one pictured in Haynes for the 1976 R75/6 that has the fuses mounted on it
BUT INSTEAD
it looks more like the board from a newer model, and there ARE NOT any fuses attached to it.
I have looked behind the fuel tank, and all around by the battery and under-seat tray.
The only thing I can think of is they whoever rewired this motorbike, stashed the fuses underneath the fuel tank (similar to my 1988 GS that has relays and other stuff attached to the frame backbone)

So I will pull the tank this weekend and take a look :eek1

thanks for the help HH....(and all others too)
dusty

Ok, it is what it is, whatever it is! For gas tank removal, turn both petcocks off and then remove the fuel lines from each petcock nipple. Don't try to pull them off, use a flat blade screwdriver to help "push" them off from the top while you pull with the other hand (otherwise you have the Chinese finger pull toy problem). Lift the seat and you'll find the two knurled plastic nuts securing the rear of the tank. Unscrew and Remove. Lift rear of tank off the tank mounts and carefully ease front of tank off the front mount. Watch for rubber bonnet on front mount, it sometimes falls away. Set tank aside.

This will be interesting. If it were me, I'd try to locate fuses first and examine, clean and replace any blown. Then test. Meanwhile, I'd take this opportunity to locate the Starter Relay (left side, main spine, near brake master cylinder). Carefully remove starter relay and its wires and clean up all the wire connectors. Well worth doing. Corrosion at the starter relay causes all sorts of electrical issues. Renew brake fluid while you're in there (assuming it's old). Clean up your ground wires on the spine and spark plug wire ends at the coils.

It could be a fuse issue, but I'm also wondering if the lack of always-on hi beam function is your new relay....if the new relay is not OEM. Some headlight relay substitutes just don't work right. Hopefully, you'll avoid having to replace the left bar switches (or did you do that already?) Let us know how the next chapter goes. This thing could be a novel.

G'day Dusty
More frustrations, eh? Sympathy attached.

You ask, "What is the "supposed indication" of 56a on the circuit board when powered up by the key?"

My reading of the Haynes diagram is that you should not get anything at 56a until you switch to high beam with the key on or use the flasher with key on or off. Could be wrong (where are the electrical gurus?)

Anyway, since I am an Autocad abuser and have been mucking around with a new wiring diagram for my somewhat modified 1974 slash 6, I took the opportunity to grab a bit more experience and cobbled together a sort of compressed map of the 1975-76 version of the pertinent bits of the diagram.

I have gone with the US version (lights always on when bike is running). My understanding is that the headlight relay in this version removes power to the headlight when the starter is operated (could be wrong again).

Here's the map



If you'd like a PDF version (high res), send me a PM including your email address and I'll send it by return message.

Now, it wouldn't be all that difficult to remove the various components from the bike and set up this circuit on the bench for testing (grab a few "alligator clip" leads to make it easier). That way you can test each component without the complications involved in testing on the bike, where any supposedly unrelated wiring errors would get in the way.

Another complication is to do with the starting safety feature, where the clutch must be pulled in before the starter button can be activated. The switch at the clutch has a Blue/Yellow wire, and a diode on the terminal board controls whether the starter circuit can be completed. This setup may have been removed from your bike, particularly if your terminal board has been replaced with a later one.

If you have found no fuses, do consider adding some. I use this arrangement to add blade type fuses:



As well as the fuses for the Green and Grey circuits, it is good to add a decent fuse to the Red wire coming from the starter solenoid to the ignition switch.

This exercise for me has been valuable - I learnt the difference between the various relays (those with 2 x 87, 87a, 87b, etc). This UK website was most helpful:

http://www.vehicle-wiring-products.eu/VWP-onlinestore/relays/relays.php

They also sell PVC insulated 'colour and trace' cable by the metre.

Best of luck.
Charlie

okay now, had some time to take "the next look" at this motorbike.
I peeled off the tank and set it aside, then I looked, and looked....AND LOOKED :eek1

I finally found out that THERE ARE NOT ANY FUSES on this one

Seriously, nothing...nada.....oh well.

So I got back into the headlight bucket, started to dis-connect some wires so I could see that circuit board better....AND SHOOT-------> That explains everything.

Those 2 slots up top I can see clearer now, and a PO attached 2 jumper type wires TO BOTH of them IN PLACE OS THE FUSES....

Hmmmm...musta' had some kind of shorting issues or something here before.

I guess I will try and remove those, put in a fuse, hook up the battery, and sit back and watch the fireworks.......any other ideas BEFORE I proceed??

AGAIN:
The wires inside the bucket all look to be in very good shape, even near new
The circuit board looks like it must have been replaced at the same time.
Wiring on the rest of the motorbike definitely appears "it's age" 1975 time.

So.....what next guys???

Dusty-
Hang in there. This will take the patience of Job. At this point, it's hard to say what has been done to the stock wiring. Are you anywhere near an airhead shop or club? If you don't have a wiring diagram specific to the 76, it's even harder. They've taken down the link for the one I had or I'd forward the link. What we think we know: the circuit board might not be stock, the existing wiring has been replaced or renewed and, to some extent modified (fuses). The fact that jumpers were installed instead of fuses is not good. Lucky the bike hasn't burned up. Let us know what happens with two 8 amp fuses installed. Probably one or both will blow, and then if you can tell us which one blows, we can begin to try to track down the short. If it were my bike, I'd be working on trying to return everything to stock. Hang in there. This won't be quick.

Fuses blow ... thus stopping excessive current.. but they are not that useful for fault finding.

For fault finding I use a headlamp globe in place of the fuse... rather than 'blow' it 'glows', still limits the current (so the wires etc will be ok) and gives a nice indication of the fault. An alternative that some use is a horn .. you may want to put a sock in it first .. and not test after dark, you do want to keep the neighbors on side. You remove the fuse and connect wires to where the fuse would be to the replacement item (globe or horn). The horn is about 10 amps, a 55 Watt globe about 6 amps, for more current both hi and low beam connected together provide umm 115 watts .. about 10 amps.

---------------------------
From Mr Bruns' wiring diagram you can see

that the hi and low beams come directly from your left handle bar switch. If one beam is working and the other is not then it could be the globe(!), the switch or the wires between the two.

That 5 pin relay for the lights
pin 30 should have battery voltage all the time
pin 85 should be close to 0 (unless the starter is operating - then close to battery voltage){if not close to 0 this could be a dirty starter motor commutator}
pin 86 should be close to battery voltage when headlights switched on {this is the control input, must be here for the relay and therefore the lights to work}
{pins 85 and 86 are connected to the relays coil - they can be swapped around without the relay or wiring complaining in any way}

pin 87 goes to the headlight globe through the left handle bar switch (and the switch selects hi or low beam, not the relay)

pin 87b goes to the tail and instrument lights

{pins 87 and 87b can also be swapped .. but don't connect them together .. can lead to problems with the parking light switch burning out.}

hey y'all

back at it again as I waited for my wife's broken dryer parts to be delivered,
but then they showed up A DAY EARLY!!! :loll

so, after fixing the dryer.....yes, she gave me a BIG-HUG
but after putting all my tools away, I jumped back on that R75/6

NEW UPDATE:
added a BRAND NEW 87b relay....LOW BEAM NOW WORKS!!

but still have issues with the HIGH BEAM & HORN:
so I pulled out the TERMINAL BOARD and tested directly on it while still hooked up,
and I find that the areas for the HIGH BEAM -56a-
and the area for the HORN -H-.........NEITHER OF THEM have power at the terminals

BUT THE SHOULD have power....CORRECT???
Those 2 points should have power AT the Terminal board with the key on & in the run position
AND THEN WHEN the handlebar switch is moved to the HIGH BEAM, or when the HORN BUTTON is depressed
the HIGH BEAM IS ACTIVATED AND THE HORN HONKS------CORRECT??


I also wiggled a bit of space around the wiring so I could get a look at the back side.....and I see that someone in the past had done some soldering down there at an open area by the bottom right area.
This is the area where 56a and 56b and Horn exists.

I do not know IF the entire board is sealed on the back side from the factory,
it probably makes sense that it should be......so someone opened it up, and did some soldering.....and 56a and HORN areas do not work.

Hmmmm.........do I need to pop for a new Terminal Board @ $109 from MaxBMW at this point????
OR
should I pull it out and open up the whole back side and see what I may be able to do to repair this-----THAT IS assuming that power should be available to the 56a and H areas (makes sense that it should).

Thanks in advance to all of those smart electrical guys that have offered tremendous assistance along the way

I'm not an electrical guru. With that in mind and armed with my wiring diagram, my answers/comments follow:


but still have issues with the HIGH BEAM & HORN:
so I pulled out the TERMINAL BOARD and tested directly on it while still hooked up,
and I find that the areas for the HIGH BEAM -56a-
and the area for the HORN -H-.........NEITHER OF THEM have power at the terminals

BUT THE SHOULD have power....CORRECT???

Yes.

Those 2 points should have power AT the Terminal board with the key on & in the run position
AND THEN WHEN the handlebar switch is moved to the HIGH BEAM, or when the HORN BUTTON is depressed
the HIGH BEAM IS ACTIVATED AND THE HORN HONKS------CORRECT??

Yes. With all of the above set as described, do you have power at the two 8 amp fuse terminals? You should.


I also wiggled a bit of space around the wiring so I could get a look at the back side.....and I see that someone in the past had done some soldering down there at an open area by the bottom right area.
This is the area where 56a and 56b and Horn exists.

Good observation. The terminal board is suspect.

I do not know IF the entire board is sealed on the back side from the factory,
it probably makes sense that it should be......so someone opened it up, and did some soldering.....and 56a and HORN areas do not work.

If all is set as above AND you have power at the fuse terminals, then I think terminal board is Tango Uniform.

Hmmmm.........do I need to pop for a new Terminal Board @ $109 from MaxBMW at this point????

Not necessarily. There are used parts outlets like RePsycle. Phone: (614) 837-1160


OR
should I pull it out and open up the whole back side and see what I may be able to do to repair this-----THAT IS assuming that power should be available to the 56a and H areas (makes sense that it should).

It seems clear that the PO has modified the wiring inside the bucket. The closer you get to restoring the wiring and circuit board (and relays/switches) to stock, the closer you are to final resolution. Hang in there. Slowly but surely you're heading toward the fix.

yes....there is power at the 2 fuse terminals at the top
HOWEVER
there ARE NOT fuses in play there, a PO put in jumper-type connectors to each set across left-to-right.


I may just unhook ALL the wires as they appear to be correctly color coded and then matched to the correct terminal.

Maybe take a real good look at that Terminal Board :eek1

on the back side, I have read, and I have been told there is supposed to be a diode down in the back of the bottom right.
I see NO-DIODE......but I do see a clump of solder and some residual brownish flux on top of the clump.

gonna be a while til I can get back to this as I am in-and-out of town next week, then for the weekend (when I do get back) gonna have the wife's brother & family here. They are good family, so should be a nice visit.
Shoot, at least I will get to go out in the forest and take them for a good dirt ride.
Me on the motorbike, them, 4-wheelers.....yee-haw!!!

As I understand it, the purpose of the single diode on the back of the terminal board is to prevent the neutral light from illuminating when the bike is in gear and the clutch lever is pulled in. Can mess up starting in neutral if it fails. That doesn't seem to be the issue at the moment, but it's just another sign of mods made by the PO. Terminal boards from '74 to '84 had that diode according to Snowbum.

http://bmwmotorcycletech.info/electricalhints.htm

hmmmm......well IT MUST BE in there, underneath that clump of solder then :eek1

more to come down the road, will include pics too!!!

.

Nothing wrong with slow ... that is what some do to have a holiday.

--------- Others for a job say
Quick
Cheap
Good

Pick 2 ... if your not in a hurry then 'Quick' is the easy one to leave out.