Author Topic: Charging issues on ‘79 G5 (Read 7882 times)

ritratto · « **on:** January 12, 2019, 05:22:25 PM »

I have replaced the diod board and the voltage regulator, checked all grounds and the brushes and charge light still will not go off. Starts easy and runs well, but put a multi meter on the battery when running and reads less than 12 volts. Ideas?

Shorty · « **Reply #1 on:** January 12, 2019, 05:37:19 PM »

Mine was doing that last week. In my case, one of the 3 prongs on the rectifier was bent down, not connecting to the yellow plug, cutting off 1/3 of the available power from the alternator. Good luck!

guzzisteve · « **Reply #2 on:** January 12, 2019, 06:20:07 PM »

What is the AC voltage coming out of the stator? Is it what the manual states?

ritratto · « **Reply #3 on:** January 12, 2019, 06:33:41 PM »

How do you check that Steve?

pete roper · « **Reply #4 on:** January 12, 2019, 06:46:21 PM »

Try flashing it. Grab a length of wire and affix one end to the battery positive then rev the engine and touch the other end to the outer slip ring for a few moments a few times and see if the light goes out and it starts to charge.

No, you shouldn't need to flash the rotor on a field excited alternator but with the Bosch system sometimes you do if the system has been sitting idle for ages.

Pete

guzzisteve · « **Reply #5 on:** January 12, 2019, 07:58:38 PM »

If I remember correctly AC voltage is checked from 2 of 3 wires or alt out put spades U, V, W. Marked on ceramic base. You check between two of them, voltmeter set to AC

Have you checked rotor for ohm's? It could have an open wire in it. I have also seen bad solder connections on wires at U, V, W (where 3 yellow wires plug in)

Kiwi_Roy · « **Reply #6 on:** January 12, 2019, 08:06:04 PM »

As Pete says
The alternator is normally flashed by just the tiny current through the charge lamp to 61 on the rectifier and DF on the regulator, if you have changed out the idiot lights for LEDs they don't draw enough current, even the old incandescent lamps were on the low side.
Some of the Guzzi with this charging system were fitted with a resistor in parallel with the charge light to boost the current.
Make sure the regulator ground is well connected.
If you pull the D+ wire off the regulator you should get a good circuit from it to the chassis proving the brushes and wires are ok, just 2 or 3 Ohms I think.

http://www.thisoldtractor.com/guzzi007/schematics/1978_G5.gif

acogoff · « **Reply #7 on:** January 12, 2019, 08:09:45 PM »

And I would check your old corroded female crimped on terminal wire ends, check for continuity with the other end of each wire and that they are not cracked and falling apart from age- fatigue or had such a high resistance that the wire has gotten very hot and failed .

guzzisteve · « **Reply #8 on:** January 12, 2019, 08:20:09 PM »

Quote from: acogoff on January 12, 2019, 08:09:45 PM

And I would check your old corroded female crimped on terminal wire ends, check for continuity with the other end of each wire and that they are not cracked and falling apart from age- fatigue or had such a high resistance that the wire has gotten very hot and failed .

This happens alot

Kiwi_Roy · « **Reply #9 on:** January 12, 2019, 08:38:48 PM »

To stop the wires corroding dip them in Vaseline before you crimp lugs on and apply it to connectors especially in wet areas, the grease protects the copper from water and oxygen.

earemike · « **Reply #10 on:** January 12, 2019, 11:36:29 PM »

I had trouble & cleaned the ignition connections and the earths - 75 T3. Not sure if your ignition connections impact this? Mine were foul so needed doing regardless.

In my trouble shooting I bypassed the regulator to see if it was faulty, I also didn’t get charge until close to 2k revs, after melting a battery I also learnt to check it peaks out under 14.2v.

When you rev it does the charge pick up at all? I had to replace my rotor/stator. BMW wrote a good help sheet to check both stator and rotor - is on the forum somewhere.

ritratto · « **Reply #11 on:** January 13, 2019, 07:36:51 AM »

Ok... a little more background... I replaced the diod board after accidentally touching the positive wire to the negative post on the battery. All was good after that. Rode it for a couple of weeks and then out one night, the charge light came on and would not go off. I checked the brushes, all contacts and grounds and replaced the voltage regulator and no change. 😫

Chuck in Indiana · « **Reply #12 on:** January 13, 2019, 07:45:49 AM »

Ok, since the charge light is on, you have power to the brushes. The "normal" failure is an open stator. If you insulate the brushes from the slip rings, you should have (from memory)

3 ohms between them. At any rate, check AC voltage at 3500 or so between the 3 yellow wires. It should be around 40 volts or above. If you have that, that rules out the alternator. Report back.

Perazzimx14 · « **Reply #13 on:** January 13, 2019, 08:23:30 AM »

Quote from: Kiwi_Roy on January 12, 2019, 08:38:48 PM

To stop the wires corroding dip them in Vaseline before you crimp lugs on and apply it to connectors especially in wet areas, the grease protects the copper from water and oxygen.

Did you know in Germany Vaseline is called Weinerslider?

guzzisteve · « **Reply #14 on:** January 13, 2019, 09:46:06 AM »

Yea, use it to lube your shaft splines, like PeeWee!

injundave · « **Reply #15 on:** January 13, 2019, 12:56:23 PM »

I had no end of problems with my T3's charging, replacing both stator and rotor at least twice each. In the end I got really annoyed and bought this

https://www.gutsibits.co.uk/pr/TheShop/index.php?q=brushless+alternator&f=d&Model=6&search=SEARCH

Since the day I fitted it (March 2017) I have had no more problems and, being a permanent magnet it does not rely on the idiot light. Money very well spent!

Incidentally, I did not have to fit the required alternator spacer as it says in the advertisement.

Kiwi_Roy · « **Reply #16 on:** January 14, 2019, 10:42:41 AM »

Quote from: Perazzimx14 on January 13, 2019, 08:23:30 AM

Did you know in Germany Vaseline is called Weinerslider?

No, but I can't wait to tell my riding buddy.

Ritratto
What happened when you flashed the rotor as per Pete's reply No 4, you should do that with the engine running. If the rotor is ok you will get a good spark off the terminal as it turns the rotor into a strong electro magnet, if the rotor is open or something wrong with the brushes of course you will get no response.

ritratto · « **Reply #17 on:** January 17, 2019, 03:00:46 PM »

I tried flashing the rotor the way Pete mentioned and no change.

What is the best method for checking the rotor to see if it is ok.

pete roper · « **Reply #18 on:** January 17, 2019, 03:10:35 PM »

Is there continuity between the slip rings? there should be.

Is there continuity between a slip ring and any of the poles of the Rotor? There shouldn't be.

ritratto · « **Reply #19 on:** January 17, 2019, 03:26:36 PM »

The slip rings being the two shiny rings that the brushes touch?

ritratto · « **Reply #20 on:** January 17, 2019, 03:30:46 PM »

I checked the continuity between the rings and yes, there is. To check to the rotor??? How is this done Pete?

ritratto · « **Reply #21 on:** January 17, 2019, 03:33:55 PM »

By poles you mean where the three yellow wires mount? If yes, then no. No continuity.

bmc5733946 · « **Reply #22 on:** January 17, 2019, 04:02:50 PM »

For most of the resistance tests mentioned the slip rings need to be isolated from the brushes either by picking the brushes up off the slip rings or insulating the brushes from the slip rings with a small piece of card board or the like, matchbook cover would do.

Brian

guzzisteve · « **Reply #23 on:** January 17, 2019, 04:19:12 PM »

Quote from: ritratto on January 17, 2019, 03:33:55 PM

By poles you mean where the three yellow wires mount? If yes, then no. No continuity.

You have to check the ohm's, same w/the rotor. Switch meter to ohm's, check w/cardboard under brushes for rotor and stator w/wiring disconnected.

Groover · « **Reply #24 on:** January 17, 2019, 04:30:45 PM »

I made an easy test diagram when I was having problems with mine. It's a bare minimum on how it all works, but should hopefully help you isolate the issue

Good luck

Chuck in Indiana · « **Reply #25 on:** January 17, 2019, 07:17:43 PM »

Quote

Another time when it quit charging the rotor checked out and the problem turned out to be corrosion in the connections, which?? I don't know. I pulled all connections to the diode panel, regulator and every connection I could find, deoxt/cleaded and it cured the problem.

I've cured *many* problems with DeOxit. Most of the time, electrical problems just want to know you care. <shrug> Take them apart, put them back together.. and they magically start working again. Some DeOxit keeps them that way.

Kiwi_Roy · « **Reply #26 on:** January 17, 2019, 09:23:04 PM »

Quote from: ritratto on January 17, 2019, 03:33:55 PM

By poles you mean where the three yellow wires mount? If yes, then no. No continuity.

You should get a connection between the terminals on raw stator where the yellow wires connect between each yellow and also between any yellow and Y
You won't get a connection to chassis unless you have a meter with the diode test function.
http://www.thisoldtractor.com/guzzi007/schematics/1978_G5.gif When it opens click on it once more and you will zoom in.
U, V, W & Y are all connected by less than an Ohm.
The wire from Y to the rectifier is optional.

How does it work
A small Voltage is supplied to the rectifier terminal 61 from the charge light
This weak Voltage feeds through the regulator electronics to feed a weak Voltage to the alternator brushes via D+ to DF through the rotor to D- and ground. this weak current turns the rotor into a magnet.
The rotor magnet, spins past the stator inducing AC Voltage into the coils, the rectifier turns this into DC to charge the battery via the B+ terminal.
The 3 small diodes on the left of the regulator rectify a portion of the AC to supply the regulator via D+ to DF, the Voltage on this wire with the motor running should be just over 12
Once the battery reaches about 14 Volts the regulator cuts back on the current going to the rotor, the Voltage coming out of U, V, W cuts back also.

Measure the D+ to DF to chassis and tell us what you see with the key on but not running then at about 1000 revs.

Chuck in Indiana · « **Reply #27 on:** January 18, 2019, 08:46:33 AM »

That's a very nice explanation, Roy. Saved in my "Guzzi stuff" file.

ritratto · « **Reply #28 on:** January 18, 2019, 02:58:23 PM »

To Pete... I checked the continuity between the isolated rings and got a connection. Then from ring to posts ( I’m guessing you mean where the yellow wires attach.

ritratto · « **Reply #29 on:** January 18, 2019, 03:03:49 PM »

I have checked the isolated slip rings and have continuity and between the rings and the posts where the yellow wires connect and no continuity.
There are so many many helpful instructions that I am really quite confused by it all. I really understand mechanics and rewired the bike myself, but as to the intricacies of the electrical system, not so much.

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Author Topic: Charging issues on ‘79 G5 (Read 7882 times)

pete roper

pete roper