G5 dull red charge light

[JayDee24ca]

First of all, I am not very savvy with electrics. Yesterday on a long high speed road trip, the bike started overcharging according to my voltmeter, with the dash charging light on dull red. I made it home okay, but shut her down quickly fearing boiling the battery.
Today I swapped out the regulator for two different spare regulators I had on hand, but there was no difference in charging, and the light stayed on dull red. Any suggestions as to what the issue might be? Diode board or alternator itself? Brushes SEEM okay from a visual inspection (without pulling them) and rotor contact ring is clean.
JD

[berniebee]

Hmm...Usually the alternator light goes on in an undercharging situation.
The first thing I would do is to verify the problem using a multimeter while the engine is running. You should see about 14.5 volts.

Usually overcharging is caused by a problem with the regulator or it's wiring. If you do see a high voltage with the engine running: Connect the negative lead of the multimeter to the frame and the positive lead to the metal body of the regulator. Your meter should read zero, certainly it should read below 0.5 volts. If you do get a voltage reading, the regulator isn't properly grounded. Check for a loose ground wire (probably a black wire.) or the body of the regulator not properly touching the frame.

If you get a high running voltage but the regulator is properly grounded, it's almost certainly a bad regulator. Not likely to be the alternator or diodes.

[JayDee24ca]

Yeah that's what is puzzling me too: the only time I have ever seen the idiot light come on is when it is UNDER charging, not over. I should have put the MM on it before I took the tank off to get at the regulator. Instead I was relying on the voltmeter. My bad. I figgered for sure that the regulator was the issue. I'll slap the tank back on tomorrow and start it up to put the MM on it and see what I get.

[Wayne Orwig]

I'm thinking diode board.
Take a meter to the diodes.

Wait.... That might explain the glowing light, but I can't imagine that making it over charge.
Confusing.

[wymple]

I rode my 84 California 2 for years with a dull, light glow from the charging indicator light. Since it always charged fine across the battery, I learned to ignore it.

[Kiwi_Roy]

Overcharging according to the bikes Voltmeter or an aftermarket one?
Perhaps confirm it with a regular multimeter at the battery terminals while running.
Check the yellow wires at the alternator and rectifier for tightness and continuity between each one, less than 1 Ohm I think between any two yellows.
(Wayne, i'm wondering what effect it would have on the light if one phase is open?)
Check the connections at the fuse box and the fuses are tight.
There are so many points where you might have a bad connection in a bike that old.
If you have diode test function on your multimeter you can access every diode in the rectifier from the terminals, refer to the diagram the large ones should measure about 0.5Volt while the smaller ones 0.6Volt open with the leads reversed.
https://www.thisoldtractor.com/guzzi007/schematics/1978_G5.gif
Too bad we aren't supposed to travel at the moment, I would love to come over to Grand Forks for a ride.

The only bike I have had with that alternator setup I upgraded with a modern regulator rectifier, Electrosport ESR450 because it also replaced all the wiring (didn't support the light though), there was nothing wrong with the original gear but I have since given it away.

[Wayne Orwig]

(Wayne, i'm wondering what effect it would have on the light if one phase is open?)

That is what I was thinking would make the light glow. But should not overcharge, right.

[Perazzimx14]

Check the ground wires.

[Old Jock]

So what Voltage did you see on the Voltmeter.

As Roy suggests, I'd check whatever you saw on your Voltmeter with a DMM as a cross check.

If you're seeing the Bulb glowing red, I'm assuming at over 2k RPM (as the system struggles below that and glowing at low or idle RPM is fine). If the light is glowing then there's a voltage difference between the battery and D+ on the rectifer, feeding the regulator which it uses as sensing system volts. Could be a failed diode that's causing the light to glow, but at a bit of a loss as to how it would allow it to overcharge. I'm not an expert nor have looked into it deep enough to understand how the system would react to all the various fault conditions

You could check to see what the D+ voltage is at the rectifier, it should be the same or very close to battery voltage

As Perazimix said I'd check the grounds on the battery and make sure the rectifier is grounded (I think it's grounded via the casing) on the rectifer and the D- on the regualtor. If the D- has a resistance that would cause an overvoltage as the rectifier would be seeing a lower voltage than the true system voltage which would cause it to overcharge.

You could check this by a jumper wire from D- on the regulator to the battery negative to see if anything changes.

Also check all the Diodes on the rectifier, there are 6 large diodes and 3 smaller diodes which feed the regulator as I remember

There are a lot of good articles on the BMW boxer charging system on the web that explain how the system works

[JayDee24ca]

I slapped the tank back on, just now and tested with the MM.  At 1800 rpm it shows 12.4V. At 3000rpm it shows 14.5V and climbing. At 3000rpm it shows 17V. And the idiot light is glowing a dull red. I checked (wiggled)  both ends of the three wire harness to no effect. This was all done with a spare regulator I had on hand.
Roy, when checking the 2 yellow 3-wire plugs for continuity, should I unplug both the alt end and the rect end before testing the alternate end, or leave one plug connected while I check continuity at the other 3-wire end?

[JayDee24ca]

Just thinking out loud now, but doesn't this system just dump excess amperage back into the ground, once it is charging at the maximum amount of 14.5 V? If this is so, then the issue may well be a faulty ground,right? (as has been already suggested) But the 17V+ output I am seeing from the MM seems to be even more than would be produced even at maximum output. Or am I totally out to lunch.

[Old Jock]

I'm taking it's the old Bosch system, as indicated by the fact its got brushes

Most bikes now have permanent magnet Alternators, so fixed output for a given RPM and the rest sunk as heat through the regualtor.

The older Bosch system is a bit more sophisticated, so more efficient, but added complexity.

It uses an electromagnet for the field, the regulator alters the field, that determines the Alternator output. I think it does this by mainly switching it on or off, I'm not sure how much it actually regulates like an analogue if at all. You'll need a wiser head than mine to answer that.

The reason for saying a faulty ground at the regulator, if the regulator is seeing less than system volts it will stay switched on until it reaches 14V across it. So if it sees less than that or none at all it will continue to supply current to the field which will leave the alternator switched on, so to speak

It sounds to me like the regulator is staying switched on the whole time, 17V doesn't sound excessive if it's not switching off.

This VERY long video where the guy is troubleshooting a BMW Boxer Airhead, explains how it all works, the Guzzi system is identical

https://youtu.be/eNpza6CjqfI

[Charles in Lake Charles]

My bet is the D- wire is no longer grounded.

[Kiwi_Roy]

That is what I was thinking would make the light glow. But should not overcharge, right.

I agree, the light would be on while the phase in question was missing.
But it's probably something stupidly simple LOL

[JayDee24ca]

Grounds are A-OK at the regulator body and regulator contact pin (D-), and rectifier/diode board.
I am thinking hard about buying another EME 32A 450W set up, especially with the US exchange rate being so favourable right now. I bought one last year for the Convert when the exchange was way low.

[Tom H]

Did you check your battery ground at the battery and where the cable attaches to motor/frame? Also might just check the positive wires there for corrosion, where they attach to the battery and the wires themselves.

Just a thought,
Tom

[Kiwi_Roy]

I slapped the tank back on, just now and tested with the MM.  At 1800 rpm it shows 12.4V. At 3000rpm it shows 14.5V and climbing. At 3000rpm it shows 17V. And the idiot light is glowing a dull red. I checked (wiggled)  both ends of the three wire harness to no effect. This was all done with a spare regulator I had on hand.
Roy, when checking the 2 yellow 3-wire plugs for continuity, should I unplug both the alt end and the rect end before testing the alternate end, or leave one plug connected while I check continuity at the other 3-wire end?

No leave the alternator end connected then you will be checking the yellow wires and the coil in series. from one yellow to another should be less than an ohm I think, anyway identical between any two wires.
These alternators control the charging by controlling the current to the rotor, its strictly analog on these old systems.
17 Volts is definitely overcharging perhaps you are not getting a good reference from the battery, the regulator is seeing it as low so its calling for a charge.

[siabeid]

On older Bosch systems, I have seen a faulty diode cause that a few times.

[JayDee24ca]

No leave the alternator end connected then you will be checking the yellow wires and the coil in series. from one yellow to another should be less than an ohm I think, anyway identical between any two wires.
These alternators control the charging by controlling the current to the rotor, its strictly analog on these old systems.
17 Volts is definitely overcharging perhaps you are not getting a good reference from the battery, the regulator is seeing it as low so its calling for a charge.

I checked continuity on the 3-wire plug at the rectifier end, with the other end plugged to the alternator, and got a 0 ohm reading between each contact.

[Wayne Orwig]

doesn't this system just dump excess amperage back into the ground, once it is charging at the maximum amount of 14.5 V?

No, once the voltage reaches 14.5 (or whatever it is) the regulator stops sending power to the rotor through the brushes. No rotor power, the magnetic field shuts down, and no more output.

So it sounds like your regulator is stuck on. But you tried a replacement regulator. I would check the voltage right at the regulator connector. If the regulator thinks the voltage is low it will keep trying to energize the rotor. I don't think it is a diode, but I would sure check them, just because.

[JayDee24ca]

No, once the voltage reaches 14.5 (or whatever it is) the regulator stops sending power to the rotor through the brushes. No rotor power, the magnetic field shuts down, and no more output.

So it sounds like your regulator is stuck on. But you tried a replacement regulator. I would check the voltage right at the regulator connector. If the regulator thinks the voltage is low it will keep trying to energize the rotor. I don't think it is a diode, but I would sure check them, just because.

Yeah, I guess its the EME unit I have on the Convert that has the shunt function on it, where excess is dumped to the frame. Permanent magnet type.
So, Wayne, checking voltage right at the regulator means while the bike is running, right? That will take a little thinking how to set that up. Maybe run a lead out from under the tank that I can connect to. I'll have a try tomorrow.

[Kiwi_Roy]

I watched most of the video John posted, it's pretty good actually.
https://youtu.be/eNpza6CjqfI

[Old Jock]

I started to wonder what regulator you used as a replacement to test it.

I have no clue what a permanent magnet type system regulator would do on the older field regualted system or how you wired it up. The regulator type required is specific to the Bosch system on the BMW Airheads and Guzzi Tonti framed bikes.

If you want to know what the max voltage the system is capable of delivering you can full field the alternator by running a temporary cable from the battery + to DF on the alternator, that will max out the Alternator output, I think 17V sounds about right.

Both Wayne and I suggested that you measure the Voltage at D+ at the regulator, it should read the same as the battery voltage or as near as dammit. Yes with the engine running at 3k RPM or above to ensure the charge system has enough revs to be operating.

As Tom H suggests making sure both battery connections are good and the main battery ground on the frame, that's also essential to ensure it all works as it should

siabeid stated it could come from a faulty diode, I have never seen that myself, but checking the Diodes is a good idea as many have suggested, can you do that?

Another stupid question but have there been any mods to the system and is the charge light a bulb of the correct wattage and is all the wiring correct and all the terminals clean.

It might be a complete PIA but unless you're confident that the system is wired correctly and all the devices are able to "see" each other, by that I mean clean connections and the cables resistance checked to ensure they are all good. IF the system has been messed with by modification, then all bets are off

Remember people are suggesting probable causes based on the system being the way it was when it left the factory, if it's not, or parts have been replaced in order to try and help you need to tell us.

Not trying to be harsh, if it sounds that way I apologize, its just the number of times threads have dragged on with everybody scratching their heads and then the OP comes back after a few pages and tells everybody about some unkown modification, is not that uncommon

[JayDee24ca]

The spare replacement regulators were Bosch and CE for the V1000. You ask about the EME permanent magnet system: that is the system I have on two other bikes, and it has a combined rectifier and regulator. It is not part of the equation here.
The bike is not all original, as I have dismantled and rebuilt the entire bike, part of which entailed ensuring that all connections of the harness were cleaned up. I have a couple of Greg Benders harnesses on it as well. I have full confidence in those.
I am going to see what a spare replacement rectifier results in, today.

[Kiwi_Roy]

No, once the voltage reaches 14.5 (or whatever it is) the regulator stops sending power to the rotor through the brushes. No rotor power, the magnetic field shuts down, and no more output.

So it sounds like your regulator is stuck on. But you tried a replacement regulator. I would check the voltage right at the regulator connector. If the regulator thinks the voltage is low it will keep trying to energize the rotor. I don't think it is a diode, but I would sure check them, just because.

Perhaps the regulator is not seeing the true battery Voltage so it thinks it's low. bad ground perhaps, measure the Voltage right at the regulator terminals,
Between + and the battery +, between negative and the chassis.

[moto-uno]

  I don't see how the rectifier can be responsible for over charging . If you have an old original
regulator ( the type with points ) you can open them up and visually check the contacts and anything else inside .
Until you find the " smoking gun " you'll just be spending money .
  If your son in law is coming back into town , I have an entire back-up system for my Le Mans that you could borrow :) . Peter

[Old Jock]

Gregg's harnesses get very good, reviews.

The EuroMotoElectrics looks like a permanent magnet single phase Alternator, similar to the Ducati system installed on later Guzzis, I don't know the full details as EME don't give out much information. Quite a few owners have completed that conversion and it appears to work well from what I've heard.

However it's a different setup to the Bosch entirely and none of the components are comaptible. Installing the EME kit replaces the whole system and converts to a permanent magnet alternator. None of the individual components can be swapped across between the EME and the OEM Bosch, that's all I'm saying

I asked about the Regulator as you said you tested the bike which is overcharging with 2 other spare regulators you had to hand and nothing changed. I was trying to ascertain if these were compatible with the Bosch charging system and not for a permanent magnet system.

Simply trying to understand what was tested, using what components and what the results were

If you tested with 2 regulators which were compatible with the OEM Bosch system and these gave similar results, then it's pretty unlikely that the fault lies with the regulator.

Perhaps the regulator is not seeing the true battery Voltage so it thinks it's low. bad ground perhaps, measure the Voltage right at the regulator terminals,
Between + and the battery +, between negative and the chassis.

From the info Roy that's what I've been thinking more or less from the get go.

If the regulator is seeing a lower voltage than the battery, then it will keep feeding straight volts to the turny bit on the Alternator which will result in too many squiggly volts on the stoppy bit.

If either D+ is lower than the battery voltage or D- is higher (bad or dirty connection) then you'll end up with more volts than you want.

[moto-uno]

^ Absolutely love your description  . Peter

[JayDee24ca]

I hate it when things are resolved yet there is no crystal clear lesson to be learned.
I hung a temporary plastic minibike fuel tank from the handlebars and ran a pigtail  out from the D+ regulator terminal to a place I could reach it with the MM once the bike was running. Tested it once without running: voltage the same as battery. Tested again, zero voltage. WHAT???? removed plug from regulator again, replaced it with pigtail, started the bike and checked again while running with the MM.
Result: idle charging 13.3 volts, and at 2800rpm 14.3 volts. Reading at battery the same. One spike to 14.6 on blipping the throttle but instantly down to 14.5 V. No red light. Perfect.
So, I can PRESUME that the fault lies primarily in the 3-way plug wire connections at the regulator. But I can't know for SURE. I hate that.  Any way, it looks like it is resolves, even if it is simply temporary. I'll check the 3-way crimps, and shoot some De-Oxit in to it, but I will be sticking close to home for a while.
Thanks for the help, all.

[JayDee24ca]

  I don't see how the rectifier can be responsible for over charging . If you have an old original
regulator ( the type with points ) you can open them up and visually check the contacts and anything else inside .
Until you find the " smoking gun " you'll just be spending money .
  If your son in law is coming back into town , I have an entire back-up system for my Le Mans that you could borrow :) . Peter

Thanks Peter, I have a couple of spare complete harnesses and associated charging systems. That is where i have been pilfering the spare test parts from.