73 60/5 electrical issues, possible short?

Good evening.

Today I spent quite a few hours of quality time with my r60/5.... On the damn driveway going over the wiring and other things!!! I should have been riding!!

Issue:.....I can hit the start button and engage the starter even when the engine is running. Discovered this accidentally. (Bad grinding noise).

How it all started:

Lately I have noticed that the battery (1 year old) can only handle a handful times of cracking the starter. Also had noticed that, sometimes, the red charging light does not come on when interesting the key.

So I started looking for a short. I got about 12.7v between battery posts. Then I disconnected the ground, with the key off, I got about 4v from negative battery post (disconnected) and frame.

Why would there be any power making it's way to the wiring and eventually the frame? That to me says there is continuity from the positive to frame and if I connect the negative battery post there would be a drain (key is off). I have the wiring diagram and traced and looked over all switches light bulbs Etc.

Started tracing wires and finally found that if I disconnect the red wire from the diode board I get 0v between the disconnected negative battery post and frame. Great!!

Thought I might have shortened the diode board. So I went to replace it with a spare one I have. Well now instead of 4v I got 12.7v between the disconnected negative battery post and frame. (Key off).

I had previously replaced the 180 watt charging system of the /5 (rotor, alternator, diode board) with a 280 watt from an early /6 (105mm stator).

The spare diode board was the /5 one without the "Y" terminal and at about 3000 rpm I get about 13.5v at battery I guess it's still charging.

Current flow

Are you saying you have a dead short in your system, draining the battery? Voltage readings and amperage readings mean two different things, amperage denotes current flow. Voltage is potential, don't whack me on the head it has been a long time since school.

You can have voltage between two points but no current flow, is kind of what I am getting at. A simple check for a dead short that will drain the battery is to simply disconnect the negative cable at the transmission and gently touch it to the transmission. If you get any kind of spark, you have a dead short in the system, there IS a drain going on. NO spark, then you don't. I don't know if an amperage meter would pick up the drain in the negative cable or not, properly attached it might. The problem is that a very small amperage draw may not register on the meter you have.

I will be in my garage today working on my RS reinstalling the steering head bearings. If I get a chance, I will look at my book on charging systems written by Rick at MotorradElectrik. This is a fine book which is out of print for now and impossible to buy new in the US. I got lucky and found a copy at Motobins in the UK.

A dead short causing current drain is most likely to be found where a wire has been rubbed and the insulation is off and the bare wire is touching the frame. This kind of a draw most of the time blows a fuse. IF everything is wired as it should be, there is no way a drain can happen. You mention you replaced the charging system. Double check your connections to be sure they are where they are supposed to be. You may not get a drain or short but you may not get proper charge as well.

The other thing to look for is do you have any kind of electronic stuff on the bike or items that require constant power like a clock or GPS? These will drain a battery.

You mention the charging light does not come on all the time when you turn the key on? That light should come on as soon as the ignition key is turned on and should only go out at about 2500 to 3000rpm. If it is not coming on, there is something wrong in the circuit it is in. It is needed to make the charging circuit of the bike work. A blown bulb, loose or dirty connection to the bulb, and your bike won't charge.

You have the wiring diagram, and you are on the right path checking to see if things are wired properly, good luck. St.

?

I don’t remember my old 73 r60/5 as having a starter lock-out. It had the old military style switches and i think the starter would engage even if the engine was already running. Maybe mine was bad too?

The intermittent charging light is a concern. Maybe the alternator brushes are getting worn?

Have you checked the Snowbum site for info on the charging system? Lots of good data there.

Edit: I remember an odd problem with the “nail” keyswitch mechanism. After washing the bike, a light was on very dimly with the key out! On investigation, I found very dirty water between the switch contacts. Blowing it out and spraying with wd-40 took care of it, but shortly thereafter I converted to a headlight bolt ignition switch.

Good luck!

Good point

Old Camper makes a good point. Besides checking for worn or shorted wires, look for obvious dirty stuff. St.

I looked at a generic electric diagram for older BMWs. It shows a capacitor near or on the diode board for interference suppression. This capacitor is connected between the battery plus and the frame. Your /5 might not have this capacitor.

A capacitor when charged, full or partially, would still show an electrical voltage between the leads. Once a capacitor is charged, e.g. with ignition turned on, there is no current running through the capacitor. With ignition off, a capacitor slowly loses its charge and slowly drops its electrical voltage to zero.

To verify that you do have a leak - a current running from the battery to the frame - here's how to verify:

If you have an older multi-meter start with setting your multi-meter to max. 10A direct current '=A'. Measure between the frame and the battery minus. You should only see a short 'blib', when the capacitor discharges and then zero Amps. If it shows zero set the max amps to a lower setting on your multi-meter like 2A. Try with lower and lower max amps settings to see how small the leaks is.

If you have a newer multi-meter -no multiple max. amp settings- then just set it to '=A'.

If this test doesn't show zero amps then you have a leak. An old capacitor at the diode board could cause this, or a device like an electric clock.

Thanks

Hey Guenther, nice catch. That makes sense and I can see a possible drain without a short. St.

I might be chasing a ghost. Battery reads about 12.6 v since last night, no drop.

Yet have to look into the charging light.

Couple months ago I checked all connections and all the wiring. Checked every single wire for continuity and any cross over to other wires in case of pinched wires or deteriorated or melted insulation. Replaced the starter feed thick cable from the battery and the grounding thick cable to the engine. Also added another grounding cable to the frame.

Fun oh fun.

IIRC, replacement non-OEM starter relays do not have the running engine starter lock out logic.

Questions

So, I have to ask, you have a standing battery voltage of 12.5? Looks good. What is the voltage reading at 3000rpm at the battery terminals? You should get 13.5 to 14.5, plus or minus a couple of tenths. Is the battery a wet cell, can you remove the caps to check for water level? If so, you can measure voltage at each section by inserting the voltage meter probe into the hole. Six cells, at two volts each equals 12, if you get a cell that is lower than the others it is suspect. What is the voltage at the battery when you are cranking the starter over? It shouldn't drop to lower then 9.5 volts. Measuring starter draw amperage means you have to install the meter in line of the flow of current in order to get a reading or, use a wrap around amperage meter. A amp draw of 100 to 150 is good.

Oh yeah, charge the battery with a charger before doing any testing. A low battery will mess up readings.

As said before, a malfunctioning charge light will kill the charging system. If it is not coming on when the key is on or when the bike is idling, or is on all the time, the charging system is not working the way it should be. First thing would be to check the bulb socket and connectors.

Rarely, a diode board can fail and still the bike will charge the battery, problem is, it will be charging AC instead of DC current. This will kill a battery. The only way to check this is to test the diode board following certain instructions.

One other thing is how old is the starter? The OM starters are pretty much bullet proof but do like other thins need occasional cleaning and lubrication. The OM starters can be taken apart cleaned and lubed but like somethings are tricky if you are not familiar with such things. Perhaps a starter rebuild shop nearby would do the job. I see a LOT of guys replacing OM starters for no good reason that could not be solved by a spot of lube and a clean. Hey, it is their money.

Good luck. St.

My thought was that using the voltmeter in this way doesn't really tell you what you want to know. This past weekend, I decided to try this on my /7 after a ride. I typically remove the chassis ground whenever I put the bike away. I used my voltmeter between the battery negative post and the engine case...I got over 12v! OK, that's interesting! As mentioned, the meter is just measuring potential between two points and each meter has its own impedance when can affect the readgins.

I asked a good friend about this. As indicated better to put an ammeter between the end of the ground cable and the chassis ground...read the amps. Another way would be to take a resistor of know resistance and connect it between the end of the ground cable and chassis ground. Now using the voltmeter, read the voltage (or potential) across each side of the resistor. Using ohm's law (V = I * R) you can compute the current flow. Divide your voltage reading by the value of the resistor...that is the current flow.

Meters

Current drain is current flow, the only way to measure current flow is with an amperage meter. The meter must be in line to read or a clamp on meter can be used. Some amp meters don't register extremely low amperage readings. Like a lot of things, the right tool for the job makes the difference. If an amperage meter does not show a drain, perhaps a milliamp meter will?

I kinda get the idea the real problem here is not so much with a drain as more of an undercharging situation or a dragging starter drawing more amps than usual. It will be interesting to see if cleaning and ensuring the charging light bulb and connections does the trick to fixing the problem. Cleaning and lubing the starter is a good thing to do from time to time depending on the bike's mileage and usage. St.

STEVENRANKIN said:

So, I have to ask, you have a standing battery voltage of 12.5? Looks good. What is the voltage reading at 3000rpm at the battery terminals? You should get 13.5 to 14.5, plus or minus a couple of tenths. Is the battery a wet cell, can you remove the caps to check for water level? If so, you can measure voltage at each section by inserting the voltage meter probe into the hole. Six cells, at two volts each equals 12, if you get a cell that is lower than the others it is suspect. What is the voltage at the battery when you are cranking the starter over? It shouldn't drop to lower then 9.5 volts. Measuring starter draw amperage means you have to install the meter in line of the flow of current in order to get a reading or, use a wrap around amperage meter. A amp draw of 100 to 150 is good.

Oh yeah, charge the battery with a charger before doing any testing. A low battery will mess up readings.

As said before, a malfunctioning charge light will kill the charging system. If it is not coming on when the key is on or when the bike is idling, or is on all the time, the charging system is not working the way it should be. First thing would be to check the bulb socket and connectors.

Rarely, a diode board can fail and still the bike will charge the battery, problem is, it will be charging AC instead of DC current. This will kill a battery. The only way to check this is to test the diode board following certain instructions.

One other thing is how old is the starter? The OM starters are pretty much bullet proof but do like other thins need occasional cleaning and lubrication. The OM starters can be taken apart cleaned and lubed but like somethings are tricky if you are not familiar with such things. Perhaps a starter rebuild shop nearby would do the job. I see a LOT of guys replacing OM starters for no good reason that could not be solved by a spot of lube and a clean. Hey, it is their money.

Good luck. St.

Click to expand...

Sorry. Work had kept me busy lately and away from the fun stuff.

I think I am good. Battery is a sealed unit and has been steady at 12.58+- these last days. Haven't had a chance to start the bike.

At hight rpm I got 13.5x volt. Don't remember all the digits. This was with the /6 alternator and the /5 diode board that does not have the extra contact Y. (I swapped them just to test when I thought I had a short). I got 9.x volt when I hit the starter button but the voltmeter was set in parallel not series.

will test the corresponding diode board and hopefully it's good and will install.

The starter that came with the bike is not the OEM .I believe it's euromoto electrics (it has the blue EME) logo on it and it's new. (previous owner had kept records and I have the receipt for it showing that it was done recently)

Have not had a chance to look at bulb and wiring.

20774 said:

My thought was that using the voltmeter in this way doesn't really tell you what you want to know. This past weekend, I decided to try this on my /7 after a ride. I typically remove the chassis ground whenever I put the bike away. I used my voltmeter between the battery negative post and the engine case...I got over 12v! OK, that's interesting! As mentioned, the meter is just measuring potential between two points and each meter has its own impedance when can affect the readgins.

I asked a good friend about this. As indicated better to put an ammeter between the end of the ground cable and the chassis ground...read the amps. Another way would be to take a resistor of know resistance and connect it between the end of the ground cable and chassis ground. Now using the voltmeter, read the voltage (or potential) across each side of the resistor. Using ohm's law (V = I * R) you can compute the current flow. Divide your voltage reading by the value of the resistor...that is the current flow.

Click to expand...

Thank you for doing the same test.

What is interesting is that with the /6 board I got 3.5 v. With the /5 diode board I got 12.5. Anyway seems like those measurements don't mean much.

Do the same test a couple of hours later without having touched the bike. I expect to see lower numbers.

If so, it's a capacitor on the bike slowly discharging itself.

Is there anything special about this lamp? Other then a 12v lamp that fits in the socket?

I just took the bulb out and carelessly mixed it with other similar lamps.

I have 2w, 3.4w and 4w lamps that fit.

Pretty good thread on charging bulbs here, from the “Tag Cloud”.

https://forums.bmwmoa.org/showthread.php?100894-Charging-Light-Bulb

Hope it helps.

OM