MOTOBRICK.COM
TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: conehead on May 28, 2015, 11:48:36 AM
-
Hi Folks,
We have been having a series of electrical gremlins on my wife's 1992 K75RT since last summer. I pulled the tank and cleaned all the connectors. Also removed and cleaned up the instrument wiring. Also replaced the TGPS. Last week we still had no neutral light, and the gear indicator was only showing 4 and 5, but the bike ran fine if we started it with the clutch pulled in. ABS fault light was on. After riding the bike around just for the fun of it, I parked it and figured we'd made some progress. But since then, the #1 fuse blows immediately when the ignition switch is turned on. No sound from the fuel injection or any of the relays. The right side of the instrument cluster is dark, and the running lights on the right are out. I'm no genius with electrical issues, clearly. Is there some obvious place to start troubleshooting this?
Thanks! Mark in Cincinnati
-
Do you mean the top fuse (7.5 Amp) for the instrument panel or the bottom fuse (15 Amp) for the horn? Just looking at my 1991 K75RT and that's how they are labelled (in German)...
-
It's the top fuse, 7.5A, for all the important stuff!
-
greetings conehead...
welcome to motobrick.com...
does it blow if you turn key ccw a notch back to parking light only...
what work has been recemtly done to this moto....
j o
-
It's the top fuse, 7.5A, for all the important stuff!
I'll take a look at my machine (with a multimeter) after I get the CFO's "chores" done...
-
Well, on the load side of the fuse it feeds:
heated grips,
power to the inst cluster for back lighting and other functions,
clutch switch,
rear brake switch,
front brake switch,
bulb monitor module,
and the parking light above the headlight.
My money is on the heated grips............
-
regarding the tgps,
See below..
edited for correction.
-
im betting rear brake wire... easy to f-up if you have had the peg plate off...
j o
-
regarding the tgps,
If it is only indicating 4 & 5, check the yellow/blue wire between the switch and the inst cluster.
Should be term #3 at the switch connector and terminal #4 at the inst cluster end.
I'd be checking for continuity on the Yellow/white wire. It controls the MSB and, if open circuit will only allow gears higher than 3 to be represented. I'm guessing a bad connection on the connector at the right hand side battery cover.
-
With a little further re-education on the BMW system theory of operation.........(thanks RBM) I also agree with Robert, check the terminations of the Yellow/White wire. Both at the switch harness end and the cluster end.
(http://i278.photobucket.com/albums/kk91/electro_handyman/Bike%20Tech/tgps.jpg)
-
Looks like you have enough info now, I'll pass to those who are more well versed than I... Good Luck and hope you solve your issue... By the way, I did fix the fence issue to the CFO's satisfaction! :bmwsmile
-
We did remove the swingarm and replace the TGPS. Since then, as the problems have shifted and generally worsened, we've just been concentrating on cleaning every connector and ground on the bike. To tell the whole story of woe would take too long. As of right now we have no lights on the right half of the instruments, no neutral or gear numbers, no running lights on the right but turn signals OK. ABS fault (which continued when we had the bike running the other day). Also no parking light although the bulb appears to be good under magnification, and no brake lights. Fuses do not blow when key is put in Park. Headlight OK. Since #1 (top 7.5A) fuse blows when the ignition is turned on, we clearly have a bike that won't start. Lots of good advice so far - much appreciated!
Mark in Cincinnati
-
Mark... Sounds like you are still hunting, I was reading an article about a fellow who used a K75 and K1100 collection of parts to build his own K75F he called it, from scratch! Pretty impressive! Anyway, he had kindly relabeled a K75 wiring diagram from German to English, which I have attached. He did not leave his name anywhere, but to give credit, his build site was at http://www.classickbikes.com/ckb/1.my.k.bikes/10_K75F/k75f.3.build.htm . That's his drawing attached...
-
His name is Drake; his id on this board is frankenduck. Duck's taking a hiatus from the online world at the moment.
If you're looking for K75 schematics, I've adapted the colour German versions from Flyingbrick (http://technik.flyingbrick.de/index.php?title=Stromlaufpl%C3%A4ne) into English. They are available on my Google Drive.
K75 basic/C/S non-ABS schematic (https://drive.google.com/open?id=0B3UPbNZRyr1raHpPeUpUeGkxM2M&authuser=0)
early K100 basic schematic (https://drive.google.com/open?id=0B3UPbNZRyr1ramNaQ19DM3Z6TTQ&authuser=0)
early K100 RT/RS schematic (https://drive.google.com/open?id=0B3UPbNZRyr1rR3dUOHBhQXp2LXM&authuser=0)
late K100 RT/RS non-ABS schematic (https://drive.google.com/open?id=0B3UPbNZRyr1rWHlMbC01eGtwR1U&authuser=0)
-
Thanks... I got some help from Drake for some LED instrument lamps, thought it sounded like him, but didn't know for sure. Thanks for the heads up, and hopefully the 92 K75RT will get sorted out...
-
As of right now we have no lights on the right half of the instruments,
This will require opening the instrument cluster and examining why some gauge lights are not working. All lights in the gauge cluster are fed from power on pin 24.
no neutral or gear numbers,
This is not a correct statement, isn't it. You stated earlier that you have "4" and "5" displayed. I'll hazard a guess that your gear shifts produce the following sequence:
Selected gear = displayed gear #
1 = 5
N = 4
2 = 6 [BLANK DISPLAY]
3 = 7 [BLANK DISPLAY]
4 = 4
5 = 5
Since the display can't show "6" and "7", a blank is displayed. This response corresponds to your previously reported symptoms (i.e. "It displays only 4 and 5"). If the Yellow/White wire was not making contact at the connector, it would appear stuck open at the gear indicator circuit. So the above gears would be registered. Check continuity in the harness connector for the TGPI under the right battery cover and at pins 2 at the cluster.
no running lights on the right but turn signals OK.
There are no running lights in the turn signal indicators on an RT. If 1157 bulbs are fitted, this might be an electrical modification by the PO.
ABS fault (which continued when we had the bike running the other day).
Troubleshoot the electrical problems, then troubleshoot the ABS.
Also no parking light although the bulb appears to be good under magnification,
Parking light is fed from fuse #2 directly. The wiring passes through the BMU connector, but it is essentially a direct link from the ignition switch to the bulb socket. If the PO fitted running lights as a modification, then maybe he tapped into the grey or grey/white wire in the relay box, or at the ignition switch. If so, you've got to troubleshoot the PO's mods first.
no brake lights.
The BMU and brake switches are fed from fuse #1 so blown fuse means no BMU and no brakes.
Fuses do not blow when key is put in Park.
...but they blow when you put the ignition into the "ON" position??
-
This will require opening the instrument cluster and examining why some gauge lights are not working. All lights in the gauge cluster are fed from power on pin 24.
You might also check the grounds on pins 10 and 23.
The ground on pin 23 handles most of the ground requirements of the inst cluster.
Pin 10, however, only provides ground for 1/2 of the back-lighting and both of the turn indicators.
-
rbm - you are correct about the gear indicator, but in the past tense. It DID operate that way after we replaced the TGPS two weeks ago, when the bike was still starting and running. But now the indicator is just always blank. In any case, thanks much for explaining the nature of that problem.
The thing is - all these new problems and fatal fuse blowing cropped up while the bike was parked overnight in a clean, dry garage, on a Tender. I am wondering if we caused them by cleaning up every connector on the bike with contact cleaner, and then putting a few dabs of Dielectric Tune Up Grease on the pins for good measure. It occurred to me in my sleep that the grease could cause a short across pins within a connector if it is actually conductive and there is too much of it slopped in there. Better Google me some grease!
Mark in Cincinnati
-
... few dabs of Dielectric Tune Up Grease on the pins for good measure. It occurred to me in my sleep that the grease could cause a short across pins within a connector if it is actually conductive a...
Dielectric grease is not conductive.
-
yes of course... not conductive...
however... do you find it seductive...
j o
-
As the grease is non-conductive, you may have globbed too much on a few connections and created your problem.