Have you check stator continuity, this is a regular failure

Posted by: @noblenobby

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Have you check stator continuity, this is a regular failure.

Yes, start with the simple stuff....

• Have you applied an electrical anti-oxidation compound during re-assembly to all the connectors you've disconnected ? The big rubber plug on the back of the Tach/Speedo housing needs those 8-10 contacts treated for sure.

• Stator and rotor continuity.

• Alternator brushes. (Are they long with lots of spring pressure being applied ?)

• Have you installed a "solid state" voltage regulator. (The OEM mechanical regulators fail all the time.)

• If your rectifier board has been converted to use the hard metal mounts, rather than the OEM rubber mounts, the 3-4" Return strap from the circuit board to the engine case in the starter well is just as important. Many assume that doing away with the rubber mounts (where the strap is mandatory) means you can also eliminate the short wire. You cannot. That strap helps make electrical connection from the rectifier Returns (attached to the inner front engine cover) to the main engine case. Depending upon an electrical connection between those 2 engine cases (separated by a gasket) is an iffy proposition.

• Lastly... is the alternator OEM ? Because a lot of the after-market "high output alternators" have serious issues after 2-5 years. Unless you're riding with a full heated suit, simply installing LED bulbs could save enough power to where the OEM alternator will do the job. The reason being that a lot of riders use a 65 to 100W incandescent headlamp bulb, whereas most LED HL bulbs only pull ~25W... while giving off more light. That's why conversion to LED is a "no brainer".

And most of all, don't forget you need to not only test for power going to the ALT bulb, but also the path the power uses to get back to the battery... the Return. The bulb can't possibly illuminate without good paths for power delivery AND the trip back home. Electrons ALWAYS buy a round-trip ticket, and your job is to fulfill their needs.

So one of the big pains with BMW bikes like yours is the bulb plug and the system it plugs into within the instrument housing. I see you checked the bulb, lol, and cleaned things up and still have the problem.

Using Rick's book is one of the best ways to track things down for fixing changing systems in the airheads.

Forgive me if I am going over what you have done already, you are not here and I can only go by what you write so don't be insulted with the following.

 Have you done any voltage checks to see if your system is putting out a charge?  That would be one of the things Rick talks about.  If you have a standing battery voltage of 12 volts and while the bike is at 2000 plus RPM, you still have the standing voltage, there is no charge. Have you done this?

You wrote you found a bad diode?  In the main diode board?   You may well have the problem there itself.

(if you take the front cover off, remember to remove the ground cable from the batter to avoid shorting the diode board out)

Seriously, if you found a bad diode, this fouls up the whole system and frankly I would look into swapping out the board or, using one of the methods mentioned in a few internet sites to check the board out of the bike.  All of the diodes in the main board have to be good.  On one hand you get no charge, also there is a chance you get a charge but it is AC not DC and your battery won't like that.

Of course check all the diode board plugs and connections as well as the connections on the alternator itself.  They are out where you can get at them.    It doesn't hurt to clean them and treat them with the stuff Richard is talking about. 

One thing to quick check is the brushes on the end of the rotor.     A stuck brush will not allow charge.  From sitting for ten years, it could have happened.

As also written it is a good thing to check any connections from the alternator diode system to the voltage regulator as well.

LOL as for me, I got sick of forty years of changing bulbs and dealing with the stock bulb mount system on my main bike and switched out to a KatDash LED system.  This eliminates all the stock bulbs and sockets and is a drop in.  I like this so much, my other bike got switched out as well.   It is not cheap and before you drop the money, if you so desire, make sure the charging system is working as it should.   I don't know how long you are going to keep the bike or how much you ride but I can say in the six years I have had the KatDash systems I have not had to fuss with the instrument cluster system at all.  This is the one aftermarket part that makes sense for older airheads.  LOL, I have no money to gain by blowing the KatDash trumpet.   

Good luck and keep us up to date on what you find. St.

Thank you guys for responding! I have done many of things you said and at the same time it gives me more info to do more testing. Definitely not offended with information and ideas to help trouble shoot. 

The KATDASH is definitely on my list! I have not used any dielectric grease to the connections yet, but will. I still have the stock regulator. 

I did test how much voltage I was making and it showed basically what my battery voltage was. 

The thing I'm going to test next are the plug pins going to the dash board. That should tell me a lot and where to start looking for a bad wires or not. Just have to find the information of what pin does what. 

This 1977 r75 is new to me and don't know any history on it. It sat for about 10 years or so and I knew that there was gong to be some problems and that is ok. I have owned two other airheads so am somewhat familiar with these great bikes but clearly a lot more to learn.

I am ordering a new diode board for sure and maybe a bypass for the generator bulb for now until I can figure out how well this bike is gong to run and then start upgrading like KATDASH, handlebars etc.

Again, thanks much for your time and expertise!

Mike

ABC 14174

Mike, save your money on the Gen light bypass, LOL, once you get things in order you won't need it and it is, unless you have a handlebar mounted volt or amp meter about the only way you will know the health of the charging system.  I had a R75/7 as my first BMW and wish I still had it.   While I never had issues with the charging system, it was nice to have the light to tell me something is wrong.

As a note of experience I have a 84R80RT now and it has the factory volt meter.  While I look at it from time to time, it was nice to have the light pop on fast at the instant my voltage regulator popped, or one of my brushes disintegrated.  Of course none of this happened near home and the flashing light gave me a heads up to check my meter to see the voltage dropping.  At the last time the regulator quit,  I was plugged in with my jacket, pants and heated grips.  I was able to shut them down and make it home on the remaining charge in the battery.   LOL, if I had perhaps waited to look at the volt meter, the voltage could have been lower and maybe I would have ended up walking home.  My now gone dealer/mechanic told me not to bother with gauges but make sure the lights for oil pressure and alternator were working.  His comment was a lot of people don't really look at gauges enough when riding and a loss of oil pressure could do damage before the person noted the drop on the meter.   Just saying.

One thing you should see about getting is one of the really good wiring diagrams EME sells.  Not only are they large, Plastic coated, in color, they have PIN numbers listed for all connections such as the big one at the back of the instrument cluster.

I will check to see if I can dig out some more information on what pins you should be looking at for the gen light bulb.  If you have continuity through that bulb from one side of it to the other, then you will have to look into the rest of the system. 

Give me a day to get out to my shop to see.  Otherwise good luck. St.

 I dug out a spare light bulb assembly.  I am attaching a picture with the two pins you need to have continuity through for the bulb to light.   I have to admit I had to fuss with it to get good contacts, here is where Richard's comments about his stuff would help.  As I wrote earlier this is a cockamamy set up and it is fussy sometimes to get good current flow when there is any kind of corrosion or the tabs have been bent too many times.

I know you bought a new diode board and that may be the problem for no charge but, You have to make certain that stupid bulb lights and has continuity to the pins in the back of the block.

There should be continuity between the top right hand pin and the second from bottom left hand pin.  While you are waiting for the new diode board check this again, as well as the circuit.

If you have the newer version of the Clymer book, page 760 shows the wiring diagram.  Blue wire and a green/blue wire are the two wires for the bulb circuit.  Trace them down and check any contacts or connections for crud or loose or broken.

Id pop over if you were near Rochester NY.  St.

Sorry my file was too big to upload and I went past the edit time.  Here is the picture.  St.

Thank you Steve! Very helpful.

I have been checking for continuity on the pins and also checked for voltage at the plug. The plug is good at least as far as I know, which isn't much on this charging system, but getting there with all the help from people like you. The continuity is iffy in the pins.

One problem I have is the strip where the bulbs go is pretty crusty. I have been trying to clean up the copper tabs where the bulbs go and seem to have got them fairly clean. I beginning to think that is my problem. Maybe a KATDASH might be in the works.

Also, with my checking connections I'm finding quite a bit of the green corrosion and been cleaning those too.  

Oh, I did check the bulbs. They all checked out good. The only one working on the dash is the oil light, which is good. None of the other lights are working at all. 

Thanks again and a great pic. Really helps to see what we are talking about.

Mike

ABC 14174

Mike, if you have that much fussing to do with the stock light assembly, ditch it and install the KatDash.  I would offer to send you one of my spare units but LOL, they were just as big again to get to work properly.

With the KatDash you will get that whole unit as in my picture. This means at least the male pins are clean.  As for the big block connector, You could try the stuff Richard is always writing about or perhaps some other kind of contact cleaner with some kind of small brush.  Sure as shooting if the male pins are bad the female ports are bad.   As for the foil strips, LOL, I can't say much but try Richard's stuff and maybe you can get them working.  

LOL, the designers of KatDash came up with the design and went into production for just the problem you are having.  Good luck. St.

Thanks again Steve! For now I'm going to bypass the gen light temporally. Now I can focus on the rest of the bike to work out any other issues. The bike is new to me and do not have too much history with it. I bought it for a kinda project for the winter.

Mike

Posted by: @14714

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I have not used any dielectric grease to the connections yet, but will. I still have the stock regulator.

Mike, please read again. I suggested you NOT use dielectric grease. A "dielectric" is, by definition, an insulator; a compound that will NOT promote electrical connectivity. (Any dictionary will tell you that.) A dielectric grease can be great on a brand new system to PREVENT contact corrosion by basically keeping water out. But you have (in vehicle years) an ancient electrical system and the corrosion is most likely already occurred. Your best bet is a compound that PROMOTES electrical connectivity.

Since the most likely cause is microscopic corrosion in the zinc electrical contact plating (IOW "zinc oxides") I suggest you will be much better served to use an anti-oxidation compound that BOTH fights the zinc oxides AND keeps out new water. In the world of pro electricians these compounds are called "No-Ox" or "De-Ox" and they use the stuff by the quart. If you know an electrician just ask, they'll tell you the same. 

Posted by: @14714

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I am ordering a new diode board for sure...

That's an expensive board! Why would you just up an order a new one ? The board is basically a 3-phase rectifier, and as such consists of 2 diodes per phase. (3 phases X 2 diodes = 6 total diodes) Diodes are easily tested with a DC Ohmmeter with 2 tests. So 6 diodes X 2 tests = 12 total tests, or about 3 minutes of your time.... versus $209 for the new OEM board. 

You can do what you want, "but as for me and my house" we will whip out the Ohmmeter. 

Posted by: @14714

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...and maybe a bypass for the generator bulb for now until I can figure out how well this bike is gong to run and then start upgrading like KATDASH, handlebars etc.

The Katdash is a great product and is one way to fix faulty bulb connectors of the OEM instrument cluster board. However, take a moment and reason with me here... The voltage regulator requires the resistance of an incandescent bulb in the ALT lamp. That is common knowledge. The Katdash uses all LED bulbs. Therefore the Katdash must, by deduction, already include the necessary resistance in its circuity to effect that same response from the Voltage Regulator. Therefore, I would suggest that you may not need both. And in fact, the presence of both may be in conflict with each other. Thus the prudent thing to do seems to be not to install an "ALT bulb bypass resistor" (or whatever it's called) until you contact Katdash. 

Lastly, just a general observation, you seem more inclined toward replacing parts rather than figuring out what's going on. I know it's frustrating, and you can certainly do what you want, but parts replacers never learn.

So what happens when you're 300 miles from home and it happens again? You can hold up in a motel and overnight more new parts, or you can get your bike towed home. However, if you've thoroughly troubleshot problems previously, then with the intimate knowledge you gained you'll be far more likely to fix it on the side of the road. "Get to know your bike at the motel" or "get to know your bike in the comfort of your own shop", your choice. 

Richard, it was noted in an earlier post, he trouble shot the system using the Rick Jones book and found a bad diode.  

Aside from his mistaking dielectric paste for the stuff you push, He has been diagnosing the problem rather than just replacing parts. 

I will agree with you that he should NOT install a bypass for the reasons I wrote about in one of my earlier posts.  St.

Thank you Richard for your comments!

I'm learning from them and have no problem with constructive criticism. That's why I'm here, to get information from others that know. I always been suspect of dielectric grease, but I have been cleaning some connectors and using it. Now, since there's about 6 inches of snow on the ground and I'm more informed, I will use contact cleaner and blow it out and find some De-Tox and start over. Thanks for that. 

As far as the bypass resistor, it is just temporary for now. The bike is new and I have no history of it other than it has been sitting mostly for 10 years. I want to find out more about the bike and then start upgrading. One problem with the dash is that many of the screws are stripped out and I can't even remove the printed board yet, being concerned about damaging the dash.

The Katdash is on my list a bit later in the progress of finding out what I have.

Again, thank you for taking the time to help.

Mike,  ABC 14174 

Mike, LOL, after years of taking my instrument cluster apart to change bulbs and address contact issues I broke out most of the screws holding things together.   Trying to find a good used housing was hard to do because most were in the same shape as my OM housing.

Siebenrock in Germany started selling the housings a few years back.  They, EME and Boxer Two Valve, have replacement housings in stock.  The kit is very nice, comes with all the screws and such.

I replaced my housing when I installed my first KatDash.  Since then, maybe 60,000 miles and several years, I have had to take the instrument cluster apart twice to fix speedometer problems.  St.