NGC - airhead charging system

[ohiorider]

Several days ago, I posted about having my battery on the R100GS die a couple of blocks from home.  In the past couple of days, I began taking some readings to try and find the cause.  This battery is new, installed last Nov, and ridden only 1500 miles.

I ran the following test on the GS battery this morning.  This was a procedure one of the Triumph forum members posted several years ago.  Before testiing, I used an Optima 3 smart charger to bring the 24ah battery back to full charge, (several hours) then ran the following:

On the charger, initial voltage read:  13.18VDC
Off the Optima charger for an hour or more:  12.88VDC
After hi Beam on/engine off for 3 minutes:  12.28VDC
After 2 minute recovery (ignition & hi beam off):  12.70VDC
At this point, battery appears to be ok.  Just checked .... it's now at 12.77vdc

Ran the following yesterday afternoon:
4pm 08 21 2020
Engine off/Ignition on – VDC is 12.75 – BATT Lite bright red. (That's what it's supposed to do)
Engine on/headlight on
1000rpm – 12.32vdc- BATT lite bright red.
2000rpm – 12.32vdc – BATT lite still very red.
3000rpm – 12.32vdc – BATT lite not as red but red.
4000rpm – 12.32vdc – BATT still won’t go out completely, very dull red at 4000rpm.

I believe the Bosch charging system in the old airheads is similar to those Guzzi used several years ago.  Don't know if their BATT lite worked the same as BMW.  I plan to bypass the voltage regulator and see if increasing rpm will result in readings up into the 14.xx range.  That should point to the regulator as the culprit.  It is an aftermarket unit that has been on the bike for 5000 miles.  Any thoughts from those of you who either own airheads or who have worked with older Guzzi/Bosch charging systems?

Thanks,

Bob

[Kiwi_Roy]

I'm guessing its a Bosch system something like this.
Check the brushes and the wires going to the field,
http://www.thisoldtractor.com/guzzi007/schematics/1980_T3_Europe.gif
Battery light should be out by 1500 revs
If you lift s brush or pull the DF wire the light should go out.
I will say I have never worked on an Airhead but I'm sure we have lots of guys familiar with them.

[oldbike54]

 According to Optima , any reading below 12.4 volts is not good , these new batteries start sulphating below that level .

 I would start there , then with the aftermarket regulator , I know the manufacturers make claims as to their wonderfullness , but experience tells me differently .

 Dusty

[Murray]

This system I belive was fitted to local GM cars that were quiet common some time ago, the reg site between the two windings (outter from memory). Similar tot he ducati system fitted to latter models it usues it case as a referance point. I would check the brushes as the previous poster stated, then the voltage reg and I cant remeber if they use a diode pack to retify or a commutator via the brushes, although the sign of a dead diode pack is typically the charge light on constantly even with the ignition off.

[Kiwi_Roy]

Out of curiosity I googled Airhead Wiring Diagram, this seems like a useful site for an airhead owner, click on an image around the outside and it throws it up in the middle.
https://duckduckgo.com/?q=airhead+wiring+diagram&t=osx&iax=images&ia=images&iai=https%3A%2F%2Fwww.rter.co.nz%2Fairhead_manual%2Fairhead_manual_images%2F217_wiring_diagrams.jpg

[Moparnut72]

I had an Airhead that did pretty much the same thing, an earlier one though. It was the brushes had worn down enough  to not make solid contact with the slip rings. Check the brushes first.
kk

[ohiorider]

Thanks, guys.  How about this approach?  You'll need some history, first.
Odometer currently shows 161,500 miles.
Sept 2014, 138,000 miles:  Installed 26ah maintenance free battery
Sept 2018, 155,800 miles:  Had Indy mechanic (Jamie, factory trained wrench) install aftermarket voltage regulator.
March 2019, 156,300 miles:  Installed 26ah lead acid battery.
Sept 2019, 159,800 miles:  Topped off with distilled water (3rd time since install.)  Battery had boiled.  Ate hole in plastic tool tray.
Nov 2019, 160,000 miles:  Installed no maint 28ah battery from Batteries Plus
Aug 2020, 161,000 miles:  Battery dropped dead while riding. 

Based on this history, I suspect 'maybe' a defective aftermarket voltage regulator that caused one battery to boil due to overcharge,  followed by new battery totally discharging while riding.  Maybe I start with a new factory regulator after bypassing the regulator that's in the bike now, and checking the reading.

[Kiwi_Roy]

Just so I can look at the correct schematic can you tell us what year the airhead is?
I assume its not the 91 GS
You seem to be going through batteries at an alarming rate.
I wouldn't use anything but an AGM battery these days.
There are good aftermarket regulators for the old wound rotor alternators.
Perhaps consider one of the electro sports that come with all the associated wiring.  e.g. https://www.electrosport.com/collections/street-motorcycles-bmw-1975-r906/products/esr450-regulator-rectifier-bmw-guzzi-bosch-alternator
Note how this particular one doesn't support the charge light. Its not the one for your bike, i just took a wild arse guess not knowing squat about airheads. But the wiring is all replaced by what they ship with the regulator/rectifier
being an integral unit there are far fewer wires anyway, almost a complete new charging system.

[PeteS]

If the stock charging system on this bike is the same as the earlier airheads it could be the diode board or the three lead harness that connects to the diode board from the alternator. The connectors overheat and oxidize and you are left with single phase instead of three phase. Single phase won't supply enough energy to both run the engine, the lights, and charge the battery. I know the later diode boards went to high temperature solder but it may be worth checking the diode pads still show a good connection to the diodes.

Pete

[Phil/TX]

Maybe check the diode board.

[ohiorider]

Again, thanks to all for your thoughts and advice.  I tried jumpering around the regulator by unplugging the 3 wire socket, and taking the advice of an airhead regular.  I made a short jumper with a crimping tool and male spade connectors, and jumpered two of the three connectors on the socket.  The regulator was totally unplugged.  Here's the instructions I followed.  Voltage did not increase with rpm, but stayed at about 12.20vdc.

To bypass the regulator, pull the tank, pull the 3-conductor connector from the regulator, put a jumper wire between the 2 connectors that are side by side, set the tank back in place and plumb up the fuel hoses. Start the motor and read the voltage at the battery as you rev the motor. If the voltage indicated continues to climb with motor revs, that would indicate a functioning charging system with a failed regulator.

Assuming I did this correctly, it doesn't indicate the regulator as the culprit.

Roy, I agree.  The bike has been eating batteries ever since I installed the aftermarket regulator.  These old charging systems aren't super hi tech, but with a good battery and not overtaxing the charging system, I've gotten 10s of thousands of miles out of previous batteries.
And yes, the bike in question is my 29 year old 1991 R100GS.

I am just no dam*ed good at troubleshooting electrical issues.  I'll need to look at connectors near the rotor and diode board next.  I have an old spare diode board that I could swap.

Bob

[wrbix]

Euro Moto Electrics website has a number of diagnostics to determine where the fault is in an airhead charging system in their tech tips section...and can supply just about any upgrade needed.

[wrbix]

Or Motorrad Elektrik:


Rick Jones at Motorrad Elektrik offers the book Classic Boxer Charging ..... if you have the inclination to order and wait on delivery.

[moto-uno]

 The system on these is the same as the Le Mans 2 and I believe the T-3 models .
You will need an ohmmeter , 1: slip a piece of paper between the rotor brushes and the rotor,
There should be around 4 ohms resistance between the rings on the rotor and infinite resistance to ground from either ring on the rotor.
2: as mentioned above , make sure the brushes are in good contact with the rotor rings ( non binding in guides , this is important).
3: check the connection at the stator(3 same coloured wires) and the rectifier for corrosion or burnt appearance.
4:these rectifiers were frequently rubber mounted and the ground wire from it to the frame(engine) may be broken or heavily corroded after time.
5: I'll bet Roy could give you a better detailed description of the ohm meter check for the rectifier :) .
6: your check with the regulator bypass will only be relevant if these other checks and components are okay.
I made no mention of checking the stator windings as I've never had the misfortune of finding one bad (on these older systems) in the decades I'd worked on them (YMMV).
Good luck , and there well could be a number of irregularities on older charging systems .   Peter

[ohiorider]

Or Motorrad Elektrik:


Rick Jones at Motorrad Elektrik offers the book Classic Boxer Charging ..... if you have the inclination to order and wait on delivery.

Good suggestion.  I talked with Rick a few days ago about just that topic.  He is out of books at the moment, and is having a small print run being made.  I need to get on the list for this book. Rick's explanations of thing electric and electronic seem to be explained in a way even I can understand.

Bob

[PeteS]

Rotors do open up. In 220k miles I went through 2. By then I traveled with a spare rotor, stator, diode board, and ignition canister.

Pete

[Murray]

A
Roy, I agree.  The bike has been eating batteries ever since I installed the aftermarket regulator.  These old charging systems aren't super hi tech, but with a good battery and not overtaxing the charging system, I've gotten 10s of thousands of miles out of previous batteries.
And yes, the bike in question is my 29 year old 1991 R100GS.

I am just no dam*ed good at troubleshooting electrical issues.  I'll need to look at connectors near the rotor and diode board next.  I have an old spare diode board that I could swap.

Bob

FFS three or four people have told you to check the brushes, the system is not charging, check the !@#$ing brushes they are a wear part before you waste anymore time.

[moto-uno]

  ^  I just figured out what "FFS" means . I just felt like saying the same thing and pop , up comes FFS . A bit slow off the mark maybe , oh well ! Peter

[Kiwi Dave]

It's quite hard to get sufficient charging voltage out of a crankshaft mounted alternator.  This applies to both the Boxer Beemers and the EV and previous Guzzis.

Guzzi solved the problem with the CARC models by mounting a chain driven alternator where the rpm could be double that of the crankshaft.

Just don't bother to upshift Bob, and run around everywhere at maximum revs!

You could also consider swapping out your lighting system for LEDs to reduce the amount of current demand on the battery.

[wirespokes]

I'm sure you know about Snowbum?

Yeah, the Guzzi and airhead parts are the same and interchangeable.

Per the regulator test it appears the system isn't charging. Although, in the original post, you said the light does dim at higher RPMs. That tends to indicate it might be the brushes or the diode board. But it could be any one of them - brushes, rotor or diode board.

And you don't really know at this point if the regulator is bad either. Only way to know is when it is charging, does it over charge?

I'd say first off to check the brushes.

If they're good, check the rotor resistance. The rotor is the most common failure item in this charging system. Sometimes it's better to substitute a known good rotor as the resistance check doesn't necessarily rule it out. It can have an intermittent open that only opens when it's spinning.

Let's see how those two checks go, then work from there.

Also, a good check on the battery is by doing a load test. You can buy a load tester at Harbor Freight and I've heard they're pretty good, but it's already connected to a good one - the engine. If, while the engine is cranking, the battery doesn't drop much below 10V then it's good. I may be wrong on the voltage, but it's somewhere in that vicinity.

All this data and much much more is on Snowbum's site.

[Kiwi_Roy]

And yes, the bike in question is my 29 year old 1991 R100GS.
 
Bob

The Electrosport ESR-450 would be a good fit then taking the place of the diode board, the regulator and a bunch of old wires for only $139
https://www.electrosport.com/collections/street-motorcycles-bmw-1991-r100gs-paris-dakar
These are manufactured in China but Electrosport a California company own the factory I believe so they should have quality control.
The rotor could be open circuit as Moto-Uno suggests although wouldn't that lead to the charge light going out Peter?
I put the ESR 450 on an old California II I had, I was quite happy with it.

As Peter says you have access to every diode on the diode board, if you have a multimeter with the Diode Test function the small ones will read ~ 0.6 Volts and the large ones will be a bit lower perhaps 0.5 Volts
If you don't have diode test a 1.5 Volt cell, a flashlight bulb in series will test the diodes you will get a lamp about half brightness in one direction, nothing in the other.
Note Peter mentioned the main diode ground as a possible problem, if you look at the T3 diagram I linked to my first reply its missing altogether off the diode board (21) LOL  http://www.thisoldtractor.com/guzzi007/schematics/1980_T3_Europe.gif
The current has to get to the battery + but it also has to get back from the chassis to the other end of the stator coils.

This shows testing the diode board with a Diode Test Meter or a simple Battery & Lamp
But if you find a bad diode will you be able to replace it, the small ones perhaps.

[PeteS]

There is no point in installing high dollar regulators, batteries or replacement diode boards unless the alternator itself is upgraded. It only puts out 238 watts. The earlier 280 watt units were barely adequite.
My '84 RT had a voltmeter on the dash. Even with the 280 watt alternator it would indicate the battery was discharging when RPMs dropped below 3500 and the halogen headlight was on. Turn the headlight off in the city and it would maintain voltage above 13 volts. Back in the day you could order the european switchgear so you could turn the headlight off. Other than installing the upgraded diode board with high temperature solder the charging system was stock and didn't eat batteries even at 220k miles when I sold the bike.

Pete

[ohiorider]

Thanks for all the good info.  And Roy, thanks for the diode board tutorial.  Common consensus seems to be 'replace the brushes.'  So .... I ck'd my maintenance spreadsheet, and see where the only time the brushes were replaced was at 95,000 miles, in July 2005.  The replacement set would now have 66,000 miles on them .....  so probably time.

Question ... is anyone familiar with this kit?  Looks like the brushes might be attached via terminal screws instead of solder.  A little more pricey than just a set of brushes, but in the scheme of things, a non issue.  If no one has used these on a Guzzi, I'll contact the company tomorrow for info.

https://www.euromotoelectrics.com/Bosch-Alternator-Brush-Kit-BMW-R-Airhead-p/boalt-brushholder.htm

Bob

[Moparnut72]

That is a super bargain as in a no brainer. I rebuilt an old Yamaha this past winter. The brushes for it's dynamo,4 of them, are almost $25 a piece. And that is just for the brush with a the pigtail. Even buying generic and gring them to fit was going to be almost $10 each. Just change out the unit.
kk

[PeteS]

The video that came up after watching this one was about installing a 400 watt alternator with high output diode board.
I know thats the route I would be taking if I had this bike.

Pete

[wirespokes]

I've ridden airheads with the stock 240 watt charging system since 1990 and now the Guzzis for the last four or five years. I haven't seen a need to buy a higher wattage system. When everything is up to snuff they work perfectly fine. However I do recall riding the R100R with the electric gloves and vest and the battery ran down, and that was on the highway. I think that one has a 220 Watt system for some odd reason. But that's the only time I had a problem, I've ridden across the country numerous times with just the stock charging system. I carry a spare rotor and diode board just in case, but the only time one was needed was when a friend's rotor died on the first day of a week-long trip we were on.

Get it sorted out, Bob, and put on another 100K. I know, getting to the bottom of a charging problem can be frustrating, especially since there's really not that much to them. They're pretty simple, really, but the way they operate can be pretty complex. I guess if you've got the money for a whole new system - go for it. But I'd do the tests and replace the bad component. If it turns out the rotor isn't bad (after buying a replacement) it won't be a waste since it's always good having a spare.

Test the brushes before replacing them! Just because they've got 66K on them doesn't mean they're worn out. This is the impetus to learn about the system - nothing like troubleshooting to boost the learning curve. Brushes are the easiest part of the system to troubleshoot so lets start there. Are you ok with a Volt/Ohm meter?

[lucky phil]

Several days ago, I posted about having my battery on the R100GS die a couple of blocks from home.  In the past couple of days, I began taking some readings to try and find the cause.  This battery is new, installed last Nov, and ridden only 1500 miles.

I ran the following test on the GS battery this morning.  This was a procedure one of the Triumph forum members posted several years ago.  Before testiing, I used an Optima 3 smart charger to bring the 24ah battery back to full charge, (several hours) then ran the following:

On the charger, initial voltage read:  13.18VDC
Off the Optima charger for an hour or more:  12.88VDC
After hi Beam on/engine off for 3 minutes:  12.28VDC
After 2 minute recovery (ignition & hi beam off):  12.70VDC
At this point, battery appears to be ok.  Just checked .... it's now at 12.77vdc

Ran the following yesterday afternoon:
4pm 08 21 2020
Engine off/Ignition on – VDC is 12.75 – BATT Lite bright red. (That's what it's supposed to do)
Engine on/headlight on
1000rpm – 12.32vdc- BATT lite bright red.
2000rpm – 12.32vdc – BATT lite still very red.
3000rpm – 12.32vdc – BATT lite not as red but red.
4000rpm – 12.32vdc – BATT still won’t go out completely, very dull red at 4000rpm.

I believe the Bosch charging system in the old airheads is similar to those Guzzi used several years ago.  Don't know if their BATT lite worked the same as BMW.  I plan to bypass the voltage regulator and see if increasing rpm will result in readings up into the 14.xx range.  That should point to the regulator as the culprit.  It is an aftermarket unit that has been on the bike for 5000 miles.  Any thoughts from those of you who either own airheads or who have worked with older Guzzi/Bosch charging systems?

Thanks,

Bob

I recall BMW charging systems from the 80's used the alternator warning light as part of the control in the charging system. If the warning light bulb failed you had no charging. It caught me out touring Europe on a brand new K100RS back in the mid 80's and left me stranded on the side of the road (well in the IOM actually). Airheads had the same system so I'm told so if the alternator light isnt working when you turn the ignition on you wont have any charging. Not sure what the effect would be for a high resistance at the charge warning light contacts or a bulb of the wrong rating would be.

Ciao 

[Testarossa]

Just LOOK at the brushes. If they're worn short it will be obvious. Replacement set is cheap but you'll have to remove the stator and solder the brush leads.

[Kiwi_Roy]

  Airheads had the same system so I'm told so if the alternator light isnt working when you turn the ignition on you wont have any charging. Not sure what the effect would be for a high resistance at the charge warning light contacts or a bulb of the wrong rating would be.

Thats a good point an LED won't work for that because it doesn't draw enough current to excite the rotor, I think they use an 18 Ohm resistor in parallel.
You haven't by chance upgraded the idiot lights to LED?

[ohiorider]

Thats a good point an LED won't work for that because it doesn't draw enough current to excite the rotor, I think they use an 18 Ohm resistor in parallel.
You haven't by chance upgraded the idiot lights to LED?

Roy, the bulb is working fine.  I understand that it is an integral part of the charging circuit, necessary to pass 'exciter' voltage.  No, I haven't messed with the idiot lite, since I understand the specific bulb is necessary to pass the proper amount of excitation voltage to the rotor.  I have the documentation to install a backup circuit in the event the bulb burns out,  Here's the title for that doc.

Installing a resistor in the exciter current circuit.  This ‘fix’ is a backup to the ‘gen’ bulb, and provides exciter current to the alternator in the event the gen bulb burns out.

Way back in July of 2005, Rick Jones sent me the following procedure for determining 'is it the bulb, or an open rotor?'  I've carried this doc in a saddle bag ever since.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Information supplied by Rick, the owner of Motorrad Elektrik – July, 2005

CAUTION:  ALWAYS DISCONNECT THE BATTERY GROUND WIRE BEFORE REMOVING OR REPLACING ENGINE FRONT COVER.  FAILURE TO DO SO CAN RESULT IN A SHORTED-OUT (RUINED) DIODE BOARD.

Hi Bob,
Your BMW mechanic has got it right-no red light with key on and motor
off means no circuit thru the rotor.  It's practically NEVER just a burned out bulb, so don't waste the considerable time it takes to access the bulb on the panel.

Here's a fail-safe test to prove the condition of rotor and light: 
- Disconnect battery ground (-) wire from battery terminal.
- Remove the front engine cover exposing the alternator and diode board.
- Re-connect ground wire and turn on the ignition key. 
- Disconnect the terminal marked DF on the brush holder of the alternator
  (black wire).
- Use a piece of wire or screwdriver stuck in the terminal and touch (ground) the DF terminal to the engine and note if the red light comes on.
- If the red light comes on, the entire charge light circuit (bulb,
   wiring, voltage supply) is proven good down to the end of that wire.

Re-connect the DF terminal, and then (with ignition key on) use a screwdriver or a coin to bridge across both of the copper rings on the end of the rotor. If this
turns the red light on, the problem is definitely an open (defective) rotor circuit. If the red light DOES NOT come on, the problem is with the brush circuit:  worn too short, sticking in their holders, or broken brush lead connections.

With the ignition off and brushes lifted up (they can be blocked with cardboard), there should be 2.8 ohms measured between the 2 copper rings on the rotor. A defective rotor will measure infinity (open).  In 30+ years of working on these bikes, I've seen maybe 2 or 3 times when the warning light bulb is actually blown. It's almost a non-problem.

To eliminate the possibility of a burned out bulb causing the system not to charge, there is a patch whereby a resistor is added in parallel circuit to the charge light so that exciter current will still reach the rotor in case of bulb failure.  I think it's posted on the ibmwr.org website in the tech archives.

Cheers, Rick