Hey there K-people!

Just wanted to drop a quick intro. I'm Adrian, currently living in Austin Texas. At the beginning of the year I got my first K-bike, a 1992 K75RS. I know this may be a little sacrilege but I'm currently turning it into a cafe/tracker project. I've stripped the bike completely down and now I'm starting to build it back up. The past several weeks have been spent shortening the frame, building a new seat pan, all new lights/indicators, and a new control cluster. 

I'm actually bumping up with a little wiring issue - electrical is my kryptonite! I've got everything pretty happy except that now I'm blowing the #3 fuse when I try to use my turn signals.

I tested, and retested each item as I put it on the bike with no issue. Then, predictably, after reassembling everything this issue cropped up. I've ordered replacement flasher relay and bulb monitor unit which I'm guessing may be the primary issue. My worry is that there is a deeper issue that will fry the new unit(s) as well. 

I had hope to post this in the electrical section but I guess I don't have enough status being a noob. 

Let me know if you have any hints.

Thanks!

Can you be more specific as to your changes to the signalling/lighting circuits?  For example, did you substitute LED signals?  Did you add headlight relays?  Did you shorten wires to accompany the shortened frame?

Did the fuse blowing coincide with a particular change you made? 

Fuse 3 is constant power and protects the instrument cluster clock and flasher circuits.  It sounds like you completely removed the instrument cluster and replaced it with an aftermarket digital instrument.  What did you do with Pin #1 on the instrument cluster connector if you did replace the cluster?

Have you checked the L/R flasher circuit for short to ground yet?.....
as I suggested in another forum earlier this day.

Hey Robert thanks for the questions, I'll do my best to provide more details.

I replaced the indicators with incandescent units and the headlight I believe is running a standard HR size incandescent. For the taillight I went with an LED 3-wire since the old tail had one light for running and another for braking. 

I've reused as much of the original wiring as possible clipping off the BMW end connectors and replacing with bullet connectors. 

I have not added any relays. 

The entire instrument cluster was removed and replaced with a digital acewell unit. 

Pin #1 (red/white) got wired to "Clock Power" on the acewell.

There is no distinct action I took that I can correlate to the problem. I tested each of the wiring changes separately. The only thing I'm not sure of is whether I tested the cluster, headlight, and signals at the same time. 

Also, I cleaned off the ground connection up front on the frame.

Inge K. - nice to see you in this forum as well - just learning my way around the k-world. 

I have not had a chance to check the l/r flasher circuit for ground yet, I'll work on that this evening. 

Do you have any tips on how to easily check, as I mentioned early, electrics are not my comfort zone.

Thanks!

As earlier mentioned disconnect the relay and all four bulbs, and then measure if you got connection between the circuits and ground.

Easiest would be to measure between the centre of one of the bulb holders and ground, check both sides.

Set the measuring instrument to resistance (ohms), you should have no Connection.

Welcome!

moose97: thanks for the welcome!

Inge: I did my best to take some readings tonight but I've got to warn you that I'm pretty useless when it comes to working a multimeter. 

I connected the black clip to the ground bolt on the frame and set the meter to 200 OHM (the lowest setting I've got). I then connected the red clip back to the ground and took a baseline reading of 0.4 – Next I pulled all the indicator bulbs and took readings from the center of the holders which were 0.5 (both sides.

Then I pulled the signal relay and took readings again from the empty indicators which now were 0.6. 

I've got no idea what any of that means, but maybe it will make some sense to one of you guys. 

Thanks!

This means that you a short to ground in both circuits L&R, you should have read
the same in the display as when the test pins isn't connected to anything......
usually "OL".

You must check your wiring regarding the new stuff you have added to the bike,
wiring to instrument direction indicator warning lamps, hazard warning indicator
(did earlier ask how you did wire that one) and the direction indicators.

Disconnect them one by one, and measure between each step...until you get the
correct reading...and found the reason to the problem.

What a great name you have. Welcome to the Knuthouse

BTW My name is Adrian

Thanks Inge

Since I am always getting a reading (even when I just check the ground by itself) would it be fair to assume that the bike is not actually grounded? I remember reading something about the ground running through the starter and those getting crudded up on older bikes. This bike has seen about 80k miles. 

I'll disconnect everything tonight and take another set of readings. 

Hey larrikin - great name btw.

Maybe you didn't have a good enough connection when you connected both test pins to ground.....you should have read 0,0 ohms....same as when you put the test pins together.

If you didn't have return path to the negative side of the battery (ground)
nothing of electric stuff on the bike would have functioned.

Your problem have nothing related to the LSR/dirty starter problem.

The objective of your tests are to determine if the hot side of each of the direction indicators are isolated from the frame ground (electrical return path).  Inge (and I) suspect that one or more hot wires on your indicator lights is accidentally shorted to the frame.  This would cause the symptoms you are seeing -- blown fuses.

To make a proper assessment, you have to first isolate the suspected wires.  The suspected wires are the ones leading from the flasher unit to each of the four indicator stalks (2 rear, 2 front).  Remove the bulb monitoring unit (BMU) and flasher unit from their sockets.  Also remove all lamps from the indicator stalks.  This leaves you with just the isolated wiring which you are going to test with the multimeter.  

Set the multimeter to a higher range, possibly Kohms or Mohms range, not 200 ohms.  You want to see a significant change in resistance and you won't see it on a very low range. Connect one side of the meter to frame ground (either under the tank or on the side of the transmission housing where the battery negative lead sits).  Test the middle of each indicator stalk lamp holder with the other lead.  Be sure you touch only the center and not the outside case.  You should expect to read very high ohms, possibly hundreds of megohms or even have the multimeter indicate "OL" which means over limit.  If you read something near zero ohms, you have a short in that indicator wire and need to trace it through the bike to find out where it is shorting to the frame.

Try this testing sequence to see if you find a wiring error.  If not, you'll need to come back to ask more questions.

Hey guys, 

So it took a lot of tinkering over the past couple evening but I think (knock on wood) I've found the source of the issue. This might sound a bit odd, but having tested every possible combination, two or three times, I feel pretty confident in my assessment. The issue would only present when I had both front and back indicators mounted to the bike and fully assembled. If I had any other combination (one signal off the bike but still wired up, or one signal with the housing opening and the bulb assembly hanging out, etc.) then the indicators worked ok. This lines up with everything working throughout multiple assembly tests and then failing after final set up. With this realization I figured that it had to be the indicators themselves. Sure enough, if separated the bulb assembly from the housing or separated the indicators from the frame things worked fine. The solution was insulating the bulb assemblies inside the indicators and for now everything seems to be happy. 

Thanks for all the help and suggestions. I'm still not sure I ever learned to read a multimeter properly but your insights were invaluable.

Congrats with the results   .
This link could become useful.

Wow, that's a great article. Thanks.