I rechecked all the electrical connections and the only questionable connection I made was to ground the wire that is prominent in the first pic. I disconnected it and you can see that it comes out of the wiring harness, is wrapped in the protective black cloth, and has an end that needs to be screwed or bolted to something. I took a multi-meter to it and it has a constant 12 volts whether the ignition is on or off. With this wire disconnected from ground, the headlights stopped working but the horn relay started actuating and the idiot lights lit up as long as I was holding the horn button.

Since it is holding current, I tried to find some place within the reach of the wire to screw or bolt it that needs a power source but could find none. Does anyone have a clue where this wire goes? Thank you in advance.

► You used the phrase "is holding current". By this I assume you mean that a 12V test lamp between this wire and the cylinder head (a good "ground" point) makes the lamp light up. If that is so, then this wire is on the "supply side" and should NOT be connected to ground. Every DC circuit has a "supply side" and a "return side" (or "ground"). So your wire either supplies 12V to do a job, or returns it to the battery. It's impossible have both functions in 1 wire.

► Secondly, if the wire you are referring to is the prominent RED wire, then it is NOT factory and has been added by the previous owner. I'm not an expert on the later model bikes, but on the rear of my 1979 ignition switch, the only terminal available for accessories is one that supplies 12V power all the time. This is the perfect place to connect accessories that have their own ON/OFF switch, such as phone chargers, running lights, etc. Trace the wire back to its source and see if it connects to the harness RED wire, either on the ignition switch or within the headlamp. In the factory color scheme, RED is the color for constant 12V power, direct from the battery.

If you are referring to the large wire with the ring terminal, you'll need to peel back the black tape to see the wire color to determine its true function. Every wire color has a single, discrete job.

► If #1 and #2 are correct, then this wire should NEVER be connected to ground or a short circuit will be in effect. This will be true irrespective of what "good" and correct things SEEM to be happening.

► The correct lamps lighting up or items beginning to work correctly may be an indication that the factory harness is NOT doing the job correctly and this wire is bypassing those issues. Therefore is merely a "band-aide" because someone didn't have the smarts or the time to find the root cause of your indicators not working. You should absolutely NOT follow their lead.

• Unless you have a purpose, such as an accessory that needs full-time power, the RED wire should be removed. It can only lead to trouble. The evidence of this statement is that it has already led to trouble.

• If you do have a purpose for the RED wire, then it requires its very own fuse. This requirement is mandatory.

• You should take the time to find the missing or faulty connection. When multiple items that don't seem to be related (eg. alternator indicator and high beam indicator), then in most cases it is a faulty return path, or what you call "ground". In most cases of faulty "ground", there appears to be a good connection, but due to micro-corrosion on the connector there is no electrical connection. In these cases, application of a product called No-Ox should be applied to ALL the connectors (front, center and rear) using a BROWN wire, which is the factory color for return paths. There are other posts detailing the use and purchase of No-Ox.

Before going any further, making my typing hands sore and possibly insulting your much higher intelligence, let's please:
• determine which "prominent" wire you're discussing
• get the supply and return terminology correct
• trace the RED wire back to its source
• find the wire color under the black tape wrapping
• leave this wire disconnected

Hope this helps. 😉

Thanks Wobbly. I put a multi-meter between the wire and ground and it reads 12 volts. Since I bolted it to ground, that is what caused my short. The question is where does this wire go. By the way, the wire I was referring to in the pic not the red wire. You correctly identified that as an after-market add which is for additional running lights put on by the PO. It does have a separate fuse and is connected directly from the battery positive to its dedicated light switch.

The wire/cable I was asking about is the one in the middle of the picture that is bent in a "U" shape. It is pretty heavy and wrapped in black fabric tape. The end is one that needs to be bolted or screwed onto some terminal which I cannot find within reach. Any suggestions?

OK, great!

You say there's 12V between this wire and "ground" with your meter, but you did not specify with the ignition switch in the ON or OFF position. You also did not specify what contact point you relied on as "ground". Since the "devil is in the details", I'd like to be sure of these 2 details.

There are 2 ways to tell where this wire goes...
• Peel the black tape back and look at the wire color. Each component gets assigned one wire color. This is by far the most definitive way. Then look on your schematic for that color wire.
• Use pure logic. If the ignition sw was OFF when power is applied, very few items are allowed power when the sw is OFF. One of these is the clock. Another might be an optional alarm system (present or not on your bike). If the ignition sw had to be ON to get a power reading, then it could be related to ignition, horns, or lighting. Besides the obvious, the "Lighting" category has several branches including turn signals, tail lamp, dash lamps, and pilot lights.

Hope this helps.

If the unknown wire is indeed a ground wire, it may well show +12V when power is applied to the other side of whatever it is connected to. The high internal resistance of a multi meter will read voltage fed through something such as a bulb. Is there a terminal to land this wire close by? I assume you do not remember disconnecting it. Is any terminal loose?
Only if the wire is brown is it a ground wire.
Good luck

Bob

The 12 volts read on the multi-meter whether the ignition is on or off. I am using the motor block as the ground. I will peel back the black wrapping and check the color of the wire and look at my schematic. I have looked at everything within reach of the wire and I cannot find anything that it connects to. I will find it and when I do, I suspect I will wonder how I every missed it.

The 12 volts read on the multi-meter whether the ignition is on or off. I am using the motor block as the ground.

Then I suspect it is as Bob has indicated. You will most probably find 2 or 3 BRN wires under the tape, and these are "ground" wires for the electrical packs on the far side of the frame.

The wire will (must) connect to one of the unpainted surfaces on one of the 3 electronic modules there. I suspect the tall module in the middle got removed to make engine removal easy. There are 2 screws facing up that seem to be on a plated surface.

Second guess, somewhere on the ignition coil body, which needs a sure return path. (This is where my 1979 is terminated.) No detail photo was provided, so I can't say exactly where or how.

Third guess, it might connect to the same bolt as the black wire for the running lights.

Hope this helps.

Actually the cable in question is a perfect fit on the lower bolt holding the Ignition Control Unit. I unwrapped some of the cable and sure enough there are three brown wires, pic attached. One wire is smaller than the other two. My plan of attack is, please weigh in if I'm off-base, is to separate the three wires and reconnect the battery. I will attach my multimeter and determine which wire has the 12 volt reading. Using the wiring diagrams, I can start isolating which components are attached to each ground wire. Once I know which components are attached to the 12 volt wire then I can begin isolating the faulty component or circuitry..

Any feedback? Thanks a lot to all for their recommendations, I've learned a bunch.

Actually the cable in question is a perfect fit on the lower bolt holding the Ignition Control Unit. I unwrapped some of the cable and sure enough there are three brown wires, pic attached. One wire is smaller than the other two.

Good. Then it is as Bob surmised, a return wire for the electronics modules.

My plan of attack is, please weigh in if I'm off-base, is to separate the three wires and reconnect the battery. I will attach my multimeter and determine which wire has the 12 volt reading. Using the wiring diagrams, I can start isolating which components are attached to each ground wire. Once I know which components are attached to the 12 volt wire then I can begin isolating the faulty component or circuitry.

Please DO NOT do this.

These wires do not function as you assume. These are not return wires pitifully short of their true destination, the battery. They are return wires than enable the electronics to function optimally. They tie the electronics group under the tank, the electronics group inside the headlamp, and the rectifier board to a single common polarity. This ensures that all the electrical and electronics devices function at the same high performance level.

Any feedback? Thanks a lot to all for their recommendations, I've learned a bunch.

With no malice toward you, my friend, but 2 simple observations...
► 24 hours ago you didn't know enough to figure out the wire's function and connection point by peeling back the wrap and exposing the wire color. Today you presume to be smarter than the entire BMW electrical engineering department by wanting to redesign the wire's attachment point. Let me assure you, on this point BMW knows best. You may have "learned a bunch", but not nearly enough, my friend. At this point you know just enough to be very, very dangerous to the reliability of your motorcycle.

The basis for your assumption is that these wires must get back to the battery because the bike runs on power from the battery. Allow me to blast this common myth to pieces by flatly stating: the bike absolutely DOES NOT run on power from the battery.

► If you want to rewire something, then rewire your running lights. That's what is wired incorrectly !! If you take power from one side of the battery with the RED wire, then you need to return power all the way back to the battery with the BLK wire. The present wiring makes the gross assumption that the ignition module mounted to the frame and the battery are at the same potential. That is a tremendous leap of faith. And is based on the second most prominent motorcycle wiring myth by assuming the frame is as good a "ground" point as copper wire. Sorry, but a copper ring lug fastened to an aluminum casting on the frame makes for a terrible return point on several counts.

Glad you got your bike back together. Go ride it.

PS. Apply some heat shrink over the black tape you cut off. The black tape is there for a reason too !

This is what I found. After fully charging and reinstalling the battery, the 12 volt reading in that cable disappeared which puzzled me for a while. I studied the wiring diagrams from one of my manuals and sure enough, the brown wires are ground wires to the frame. I retaped the wires and installed with the bolt I originally used. The strange symptoms continued; idiot lights not working except for intermittent neutral light, turn signals and horn not working. Further study of the wiring diagrams led me to two circuits which led me to believe that something in common had to be the cause. After using my multimeter to test the two circuits, I was led to the fuse box. All four fused looked good visually but I pulled and tested the four fuses with the multimeter; all were good. I checked the wiring to the fuse box and found that all four wires were badly crimped. I checked continuity on all four wires and found the two rear wires were severed and had intermittent contact. I repaired all four wires and all systems are go.

this may help some who don't have a copy. :cheer:

https://www.airheads.org/index.php?option=com_content&view=article&id=302:wiring-color-codes&catid=12&Itemid=140