R60/5 '71 - Loss of power red charge light illuminated at 40mph

A thought

Hey Kurt, I understand fully what you are saying about the battery. In my long winded possibly incorrect (hey, I don't know it all, LOL) writings I mention the battery or some kind of energy from the system is needed to "energize" the alternator. This is one of the main differences between generators and alternators. I am not going to go into the other differences between the two.

I have not tried running a bike without the battery connected. With a point system, I might be inclined to try it just to see what happens. However, my one bike has an ignition module and my other has a Boyer Point replacement system. I don't want to invoke the gods of popped ignitions by trying it on these bikes. My luck, and I would be struck down with a blown module on the RT or a dead Boyer on the RS.

Perhaps, one of our more daring airhead owners who have bikes with points would be so kind as to try this to see what happens? If they do, I claim no responsibility for the results if they turn out bad.

Just to add, I mentioned the diode in the charging light system. Does it block current flow in one direction? I mean if the light circuit was energized all the time, the light would be on all the time. Something blocks current to the light when the system is charging and not running off the battery. Conversely, when the voltage drops, and the battery which is at a slightly lower voltage than the charging system kicks in, the current flows to illuminate the light.

The charging current to the battery is nearly always higher than the standing battery charge. Charging values should be 13.8 to 14.8 volts. A resting battery may read 12.5 or so when in proper condition. So, when the charging system at a higher voltage drops out of the system, the current at a lower voltage in a different path, kicks in. Our little diode says, OK current flow to the light.

I am sure some engineer or smarter person is reading my stuff and is shaking their head. I don't have much book learning, just a long time of experience. St.

Never heard of a diode in the charging circuit for this function. I've boiled the system down in my mind to the simple discussion I mentioned...the bulb is just there to alert the rider when the voltage on either side is not the same. I could be making that too simple.

let me get out the schematic

Hey Kurt, I have done my usual nonsense, I should have checked the wiring diagram first before writing.

I COULD BE very wrong on my drivel about a diode in the system. I will check now and get back. St.

Did a little investigation

Hey all, Kurt,
I should have looked at a schematic for the bike in question.

So, the charge indicator bulb according to my Chilton's schematic shows one connection of the indicator bulb going to one side of the rectifier. The other side goes too somewhere in the switch. When looking at my bike's schematic, which is much different, I do see a diode (although not named as such) in the line.

So, getting back to what I have been saying, something has to control current flow through the indicator lamp. In the case of this bike, the current flow through the lamp is handled inside the rectifier, most likely with a diode of some kind.

In my bike, there is a diode in the system (or I assume it is a diode, better schematics might name it as such) blocking current flow from one direction. When the current is flowing properly while the alternator is charging the light is out.

Light bulbs don't know anything about voltage or flow of voltage. They light up regardless of the voltage applied to them and they don't care which side is hot or ground as long as there is flow from hot to ground. A diode (and someone with more knowledge is welcome to educate me on this) allows current flow in one direction only blocking it from the other direction.

So you see, in my addled mind, this makes sense. While the alternator is charging and its voltage is higher than the set point of the diode, the light stays out. When the bike is running on the battery at idle or the alternator is not charging, the voltage is below the set point of the diode and current then flows to the bulb to illuminate it. In this bike, that may take place in the rectifier.

I am enjoying this back and forth very much and I waiting to hear what the solution is. St.

Well, maybe an expert can explain things properly regarding the circuit. In looking at Motorrad Elektrik's Classic Charging booklet, there is no diode shown. I'm not sure if you're thinking about the diodes on the diode board. The light in the headlight has two wires to it. One wire goes through the starter relay and connects to D+ on the diode board...this represents the voltage output. The other wire goes through the ignition switch and has a path to the + side of the battery. Snowbum discusses this on this page in the "How it all works" section:

https://bmwmotorcycletech.info/trbleshootALT.htm

Of course voltage doesn't "flow" but current does. Current flows when there is a difference in voltage. My thought is that's when the bulb lights up, when there's a difference in voltage.

It is far simpler than what I am reading here. One side of the bulb is connected to the battery. The other side is connected to alternator output at the alternator hot brush. With no charging, current flows from the battery, through bulb and it illuminates. As soon as charging voltage equals battery voltage the alternator output is at the battery and also at the rotor hot brush. So the bulb goes out.

The charging indicator bulb has one side connected to battery plus and the other side to the output side of the small diodes on the diode board.

With the motor stopped the bulb gets plus from the battery and minus thru the diode board. Once the motor becomes alive the diode board now provides a positive voltage on that wire. Once the voltage from the diode board gets close to the battery voltage the charging light extinguishes.

The output at the diode board can never be higher than the voltage on the battery plus wire. Why? Because the power diodes on the diode board are connected to battery plus, the path that charges the battery.

The diode board wire connected to the charging bulb comes from a set of smaller diodes on the diode board just for the purpose to provide the feed back to the voltage regulator so it can adjust the charging voltage.



/Guenther

I knew someone would educate me

Hey Guys, thank you so much for explaining how the system works as well as doing it in a way that makes sense.

I admit I had a little bit of knowledge (just enough to be dangerous?). You have filled in the obvious gaps in my mess of knowledge and I admit, it is a mess.

Kurt, yes, you are correct current flows, as I have said, I think of it like water sometimes it makes better sense.

Yep, there is a diode involved but it is not doing what I assumed it was doing. Never assume anything, LOL. Bottom line, I can now see and understand just how the current flows to provide energy to light the bulb.

Still, that would explain the red light coming on, but what about the loss of power? Nah, I am not going to go there any more than to check the switch. Seems there is an article on the R60/5 switches in the Internet BMW rider's web site.https://ibmwr.org/index.php/2018/07/14/bmw-5-ignition-switch-removal-repair/.

I know my brother in law's bike had a bad switch causing the same problems. Now I really want to know what the problem in this bike is and what the solution is. Thanks again all of you guys for putting up with me and being polite. Cheers, St.

Looking at Paul's reply I realized I made a mistake in my description. The minus side of the bulb comes from the voltage regulator and then through the rotor/brushes to ground - as Paul said.

So for example if one of the brushes no longer connects to the rotor's slip ring the alternator can no longer provide the requested output voltage, aka no charging. But the charging indicator in this case is off - no ground at the bulb - and you think the system is still charging.

About the "loss of power" - I assume we'e talking about electric power - could be with the kill switch in the off position or a failure in the kill switch. But with a problem in the kill switch ALL lights are out inclusive the charging light.

Some riders call the ignition light the 'idiot light' because it does not reliably tell you that the system is charging.

/Guenther

Clarification

Ok, Gunther comes along and makes a point, loss of power, what does the author of the thread mean by that? Again I slap my forehead and tell myself never assume anything!

I have been harping on looking at the switch because I "assumed" loss of power meant loss of engine power. That is what was happening to my brother in law's bike, it would cut out, run rough, the red light would come on and it was due to something messed up with age and use inside the switch on top of the headlight, the ignition switch.

If it is in fact loss of charging power, of course the problem is in the charging system.

Geeze, I am getting dumber each month that passes, I better stop giving advice and just stick to riding. LOL. Cheers, St.

It's not you it's me

Hi Steven, Kurt, and everyone else who has chimed in on this and provided such incredibly valuable and detailed information.

To begin with I'm sorry if my OP wasn't specific enough - I did indeed experience a loss of engine power when the light came on. I'll try and recreate the circumstances with greater precision..

1. Riding along at roughly 40mph 4000RPMs when the red light comes on and I begin to experience a loss of engine power. Other lights and signals remain operational at this time.
2. Continue riding for another mile or two with engine power behaving erratically and not corresponding to throttle input.
3. Pull over about a mile down the road when it is safe to do so, and as soon as I slow to a stop and release the throttle engine cuts out and all electrical power shuts down (no lights of any kind with the key plugged in).
4. I pull the key out and reinsert it a few times and still no indicator lights and no electric start.
5. While the key still inserted I attempt to kickstart it and the engine turns over and starts up - still no lights of any kind however.
6. I ride home with reduced and fluctuating engine power and still no lights.
7. I arrive home and when I pull into the driveway - magically all lights come back on and everything seems fine.

I spent yesterday afternoon riding around the neighborhood and can't manage to recreate the problem with the voltmeter attached to my handlebar (not much variation reading 13.05 to 13.25 most of the way). I think I will need to take it for a longer ride at varying speeds and RPMs to hopefully recreate the issue when I have someone to follow in my truck (just in case I get stuck).

If nothing else, through all of your generosity in terms of imparting your knowledge and expertise I have learned a lot - so many many thanks. I will continue to trouble shoot beginning with the switch and the wiring in the headlamp and keep you all posted. cheers, david

STEVENRANKIN said:

Ok, Gunther comes along and makes a point, loss of power, what does the author of the thread mean by that? Again I slap my forehead and tell myself never assume anything!

I have been harping on looking at the switch because I "assumed" loss of power meant loss of engine power. That is what was happening to my brother in law's bike, it would cut out, run rough, the red light would come on and it was due to something messed up with age and use inside the switch on top of the headlight, the ignition switch.

If it is in fact loss of charging power, of course the problem is in the charging system.

Geeze, I am getting dumber each month that passes, I better stop giving advice and just stick to riding. LOL. Cheers, St.

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You should be able to ride a couple hundred miles with no charging system on a good fully charged battery. Red light came on..no charging so there must have been a dead short or bad battery. But you said after a later ride, the battery was fully charged and holding. I'd be looking for a short..something that can drain the battery in a short period of time...and do a load test on the battery.

Thank you Greg - will do. d

beemerguru said:

You should be able to ride a couple hundred miles with no charging system on a good fully charged battery. Red light came on..no charging so there must have been a dead short or bad battery. But you said after a later ride, the battery was fully charged and holding. I'd be looking for a short..something that can drain the battery in a short period of time...and do a load test on the battery.

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From a diagram I have for the R60...R75/5 for the 1969 models and up:

One fuse in the headlight compartment is for the indicator lights and also for the starter relay (green/black). Maybe there's a problem with the fuse, fuse contacts or the green wire that goes to position 15 of the ignition key.

It could explain why the indicator lights are off and the starter did not work.

The same position 15 at the ignition key would still supply 12V to the ignition coils. So the kick start worked.

For the charging light temporarily to come on it could be the brushes of the rotor not touching the slip ring or have a lose soldering point. No idea how that could cause a slight loss of power at the motor at the same time.

The charging voltage of 13.05V to 13.25V is OK at idle but should be closer to 14.0V above ~2,000 rpm. Could you start the engine later on with the starter and without having re-charged the battery?

/Guenther

Thanks for your reply Guenter. Unfortunately I have an early model /5 so it came equipped without fuses (I believe they were added in '72 but I could be wrong about the date). But the more I delve into this and the more feedback I get, the more I think that maybe it is simply a short somewhere (or a switch issue) which could explain most of the issues I experienced (with the exception perhaps of loss of engine power).

And yes I was able to start the bike later using the starter. I am going to do a load test on the battery and check over all of the wiring in the headlamp as Steven and Greg suggested earlier when I'm home from work this evening. d

Guenther said:

From a diagram I have for the R60...R75/5 for the 1969 models and up:

One fuse in the headlight compartment is for the indicator lights and also for the starter relay (green/black). Maybe there's a problem with the fuse, fuse contacts or the green wire that goes to position 15 of the ignition key.

It could explain why the indicator lights are off and the starter did not work.

The same position 15 at the ignition key would still supply 12V to the ignition coils. So the kick start worked.

For the charging light temporarily to come on it could be the brushes of the rotor not touching the slip ring or have a lose soldering point. No idea how that could cause a slight loss of power at the motor at the same time.

The charging voltage of 13.05V to 13.25V is OK at idle but should be closer to 14.0V above ~2,000 rpm. Could you start the engine later on with the starter and without having re-charged the battery?

/Guenther

Click to expand...

No power

leighland said:

Hi there - I recently got my '71 R60/5 back on the road again after 4 years in storage. During the first ride yesterday at around 40mph the red charge light came on in the headlamp assembly and I began to lose power. When I pulled over to the side of the road the engine stopped and all lights went out. I figured it must be a faulty alternator/rotor as the battery is new and didn't think it was a short in the system because of the way the charge light came on and loss of power when I was riding. The starter wouldn't work and no indicator lights appeared with the key fully inserted - but I was able to get it started using the kick starter, and drive it with limited power at my disposal. I had no lights (turn signal, headlamp, indicators, etc.) on my way home, but when I got home and parked it in the driveway strangely everything started working again perfectly. It worked fine today for a quick 3 mile ride around the neighborhood but I obviously don't want to chance taking it for a longer ride until I get this sorted. If anyone else has experienced something similar please let me know, I figure I will need to test/replace the rotor/stator, diode board, and v regulator, but if I'm missing something more simple/obvious I'd appreciate any advice you can offer. Thanks so much.

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New battery but what did you buy? Not one of those cheap Chinese knock-offs I hope.

My brother in law had similar problems with his /5. You would turn on the ignition and watch the voltage (using a DVM across the battery), quickly go from 12.6vdc, down to below 7vdc. Took the battery to an auto parts store and of course it failed the load test.

They sent him a replacement (same Chinese POS), and same problem.

Finally put an Odyssey in and problem solved.

These bikes are very, very simple as far as the electrical system, so it's just a matter of starting at the last thing you did and working from there.

Chinese Batteries

RPGR90S makes a good point regarding Chinese batteries.

Over the years, my local airhead shop installed various batteries they ordered and stocked and customers provided themselves. The amount of trouble caused by so called good batteries failing drove the owner of the shop nuts. A couple of years ago, he stopped selling (unless his customer demands) any batteries except Odyssey. Since then, he has NOT had a battery failure problem at all.

On a side note, a fellow brought his R1200RT in for an oil change and state inspection. Upon my friend trying to start the bike, turns out the battery was dead. Where did this battery come from? Pep Boys! Also, the battery was not even two years old. So, the owner of the bike is going back to figure out what to do about his dead battery as well as find out what caused it. (my friend only works on airheads, he doesn't have the computer stuff to work on the 1200RT.)

I myself would think if a battery has an internal short, when it failed the lights and everything would go out. Hey! I have seen a lot of stranger things happen because of bad batteries so this might be something new to add to the list of weird battery failures. If it is in fact the battery is bad.

Good luck on the hunt for the problem, and please let us know what you do find. Cheers, St.

STEVENRANKIN said:

RPGR90S makes a good point regarding Chinese batteries.

Click to expand...

So, other than Odyssey, what batteries can I reliably count on to have been manufactured in the United States? There is so much rebranding and labeling going on I can't keep track. So what is actually built here?

American Batteries

Hey Paul, I understand the dilemma of buying a good American made battery. Someone in another thread mentioned a company in Pennsylvania. Forgive me, I have forgotten the name just this second. When I asked my shop owner if he had ever investigated them as another source beside Odyssey, he said he had in deed done so. His investigation as far as he was able to deduce is the industrial batteries, and car batteries are in fact made in PA. The tractor and bike batteries are outsourced and branded.

Shoot, for all I know Odyssey does the same thing. All I can say is since the shop took to stocking and selling Odyssey, there have not been any returns or problems due to the batteries. Not so all the other maker's stock.

No, I don't get a commission or kick back from Odyssey, LOL, I wish I did. I guess the bottom line is, cheap gets you cheap, beyond cheap, is still a gamble but the odds are better you get a better product. Cheers, St.

I install 2-4 Odyssey batteries a month and have taken a big collection of cheap, fairly new batteries that failed the float test. The 2 year Odyssey warrenty is nice too.

I've had some customers get black plastic blocks to take up the extra space in the early battey boxes and drilled big holes in the bottom to stash paperwork and extra cash for long trips. Wooden blocks work well too but plastic is way cooler.