Generator Light Comes On, I lose Turn Signals and Brake Light

[neithardtm]

Hello, I am new to street bikes(dirtbikes all my life) and I recently purchased a 1974 R90/6 and have been making improvements. Since I have had the bike I have had issues with the generator light and the lights on the bike working properly keeping me from riding at night or that often in general. When I start the bike, the light will come on in the first minute and I lose all lights but headlight. I have no turn signals or brake light when this happens. I recently installed the Enduralast charging system to spec and am still having this same issue. New rotor, stator, diode board, brushes, voltage regulator and I was told the battery was new when I bought it. The date code is 03/21. The Battery with the key off is reading 12.76V and when it is running with just the motor(no lights or anything) it reads up to 14.32V at about 3000 rpm. I am testing this at the battery itself. From everything I have read, it sounds like it should be charging properly reaching over 14V. I am hoping someone here can point me in the right direction in what to test or look for and why the light is coming on and why all my lights cut out when it does. Thank you, Mike

 

[69zeff65]

Check your grounds

Check all the ground locations specifically the main ground from the - battery terminal to speedometer pinch bolt. Second check your battery cables for signs of corrosion or deterioration of the connections. Sounds like there's a ground problem here.

 

[stevenrankin]

Wiring

Well, the readings you are getting at the battery tell me the charging system is working as it should be. So, I would concentrate on other wiring issues elsewhere in the bike. I would suggest you contact EME online and buy their very good large color plastic laminated wiring diagram for your bike. You will drive yourself crazy trying to solve your problem without it or at least a good wiring diagram. Unlike the wiring diagram found in the Clymer books which are in color, the EME version also in color has the terminal numbers for relays and switches and things listed on the diagram.

The first thing to check and is not exactly easy to do is check the circuit board inside the headlight housing to be sure proper wires are plugged into the proper place on the board. Everything is color coded so if you find a black blue wire plugged onto a terminal that is gray on the board, you have a problem if you get my drift.

Same thing goes for the ignition switch, the switch has three positions as far as I know. Off, parking lights and full on (all lights and ignition work). It is possible to get a wire misplaced on the switch because the switch terminals are not color coded to match the wires going to them. The switch is stamped with terminal numbers next to each terminal and that number corresponds with the proper color wire. The EMW diagram will show this relationship. The original black and white BMW diagrams will also show the terminal number and proper color wire but they are in German and black and white. Color is so much better.

So after all my stuff, your problem could be something very simple. If you are blowing fuses depending on which fuse helps determine the parts of the system faulty. Again, a good diagram will show this. It is possible to have a wire out of place and the charging system will work, the bike will run and some things will work fine.

You didn't say if the previous owner did any kind of wiring changes to add lights or stuff? Beware of non factory wiring or cobbled things. It is possible you have been bitten by what I call previous owner's disease. Some previous owners pass off their mistakes or downright nonsense on to the new buyer for various reasons. Sadly, the new owner many times has to sort things out in order to make things right. Hopefully in your case, it will be a cheap fix. Anymore information you can provide may help find a fix for you. Good luck, St.

 

[neithardtm]

All the ground wires from the battery to frame are new heavy gauge wire I cleaned up the contacts. I do have some issues with the ignition switch. It doesn't always turn on properly. I have to cycle it on/off sometimes to get it to activate the lights on the cluster. I am ordering one of those as soon as possible. I had not taken the headlight assembly apart yet to check the wiring inside. I didn't think the issue could be in there but now after your comments, it could definitely be suspect.
It doesn't appear much was changed from the previous owner. It wasn't running right when I purchased it. I found one of the throttle cables in the throttle housing was not in the guide and was seemingly only engaging one carburetor due to not pulling both cables. I changed the cam and throttle tube and rebuilt the carbs completely with all new gaskets/jets/floats direct from Bing. It now runs amazing after I adjusted the valves. Just these pesky electrical issues. I will have to check the board in the headlight bucket and check for fuses. I am not aware that I have blown any fuses or that any were blown but definitely something to check. Thank you for the input.

 

[stevenrankin]

Ignition switch

With more information I narrow things down. If you are having a problem with the ignition switch, that may be your only problem. You will have to take the headlight out of the bucket to change the switch unless you have a fairing and it is mounted in the fairing?

So, since you have a new switch on order and have to get into the headlight shell, now would be a good time to just check the wiring on the back of the switch and the board. I will check to see if I have a wiring diagram for a R90/6. Perhaps I can give you the terminal numbers on the switch and the color wire to them. Like I said, all of the wiring inside the shell is color coded and should be matched color for color on the board.

Cheers, St.

 

[neithardtm]

I do not have a fairing. I removed the headlight, checked the fuses and they are both closed. Ignition switch is progressively getting worse. After my past two rides, pull in the garage, turn the switch off. If I try to turn it back on again within about a half an hour, it does not come on. Headlight comes on normally in all 5 positions and different modes but none of the cluster lights illuminate at all and no power to the starter. I tried every few minutes after this and it seems to takes about a half hour before it will work again. And works every time after this until I start and ride again.

During the ride today, all my lights worked perfectly, no Gen light until about 6 minutes or so of riding. Headlight on the whole time, turn signals work fine. Then I hit another turn signal, the signal does not work, signal light on cluster goes out while Gen light goes super bright any time I touch a brake or activate a turn signal. I turned the signal off and the Gen light goes dim until I hit the brake or try a signal which neither ever actually flashed/came on when used. I immediately checked the battery when I parked and had 13.12V

I should be receiving the switch Tuesday or Wednesday. Unfortunately no where close to go pick up from. I will be installing the day I get it, will update accordingly. Very strange stuff going on.

I can also note that when I bought the bike two months ago, I immediately drove it to the dmv and it passed inspection fine. It was about a 35 minute ride. I sat in the inspection line for 15 minutes at idle, all worked perfectly.
Has progressively gotten worse since I began riding it more and more. I had only changed the spark plugs/wires, throttle tube and cam, and rebuilt the carbs.

Thank you for all the help.

 

[stevenrankin]

Wiring

Well, at this point I would again suggest getting a good wiring diagram just in case the new switch doesn't do the trick.

Check the connections on the starter relay under the gas tank. They are prone to corrode especially if the master cylinder leaks on it.

Without a good wiring diagram, there is only blind luck to figure out what is wrong. Sorry I can't be more help, I haven't been in the garage to check my diagram maybe tomorrow evening. St.

 

[neithardtm]

Wiring diagram

I do have the manual from bmw, got it a few days ago. I did check the board and it all seems to be connected properly. Very hard to read out of that book. Been taking photos with my phone to be able to zoom in and it helps.

 

[stevenrankin]

I know

I know, working in the headlight bucket with all the wiring is what I call taming a bundle of jumping snakes. I don't know about your bike but my two have a few extra harnesses in there for hazard flashers and a clock and voltmeter. Just makes things more interesting and tighter.

Well, the good news is that if you didn't find anything off peg in the headlight, your new switch most likely will be the solution to your problem. Just remember when you get it, to wire it with the proper color wire to the proper number terminal. It has been awhile since I looked at a BMW wiring harness in the repair manual, I think they are in black and white with color codes spelled out. They also give terminal numbers for things such as the switch and relays. Makes things somewhat easy.

Good luck, it sounds like you are getting near to riding problem free again. St.

 

[neithardtm]

Fixed, not how I thought.

OK, so I changed the ignition switch. I received it a day early. Upon hooking the battery up and turning the key on, it did not immediately work and I had no lights on the cluster. I checked all the wiring and it was correct. I did some more digging and even though I had checked the fuses on the board in the headlight, I didn't clean them up or remove them. I removed both of them, cleaned up the ends and the spade clips, and tried again. Instant success. All lights came on, bike started right up, and worked flawlessly for the next 2 hours of riding. All brake and turn signals worked properly the entire time and It had been fixed. Thank you for all the help.

 

[stevenrankin]

Congratulations

Thanks for letting us know how you made out, and congratulations. Have fun riding now. St.