Author Topic: T3 charging question  (Read 352 times)

Online Tkelly

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T3 charging question
« on: December 02, 2021, 07:29:49 PM »
The charging light doesnít go off until I ride several miles,is the bike not charging or is something wrong with the light.No problems otherwise.Any ideas appreciated.

Offline lucian

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Re: T3 charging question
« Reply #1 on: December 02, 2021, 08:23:17 PM »
Do you have a volt meter you could hook up to the battery?  You should get 13 to 14 volts with the engine revved up a bit 3,000 rpm or so.  My LMIII did the same  until I cleaned up the slip rings on the alternator. If it is charging and the battery doesn't hold it it's probably time for a new battery.

Offline n3303j

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Re: T3 charging question
« Reply #2 on: December 02, 2021, 08:48:29 PM »
Might want to check that the brushes are not worn to the point of intermittent contact.
Stock voltage regulator might be giving up the ghost.
EME solid state is a good & cheap replacement.
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Online Kiwi_Roy

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Re: T3 charging question
« Reply #3 on: December 02, 2021, 09:21:13 PM »
The charging light doesnít go off until I ride several miles,is the bike not charging or is something wrong with the light.No problems otherwise.Any ideas appreciated.
https://www.thisoldtractor.com/guzzi007/schematics/1980_T3_Europe.gif
I would say its not charging while the lights on, the D+ terminal is much lower Voltage than the battery Voltage.
Once the rotor is energized enough the 3 small diodes in the rectifier overwhelm the Voltage from the light and turn it off
The charge light on my convert barely provides enough current to energize the rotor, I tried adding a second bulb in parallel and it seems to start charging at lower revs.
Some Guzzis have a resistor in parallel with the lamp or just a resistor where the lamp would be, this can provide a much higher excitation current.
I'm not sure what value the resistor is but I would try something like 20 Ohms 5 Watt
« Last Edit: December 02, 2021, 09:30:07 PM by Kiwi_Roy »
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Re: T3 charging question
« Reply #3 on: December 02, 2021, 09:21:13 PM »

Online czakky82

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Re: T3 charging question
« Reply #4 on: December 03, 2021, 04:40:29 AM »
Hey Tom, your brushes are fine. You have an LED Gen light. I used a resistor in parallel for more resistance as Roy stated. You can swap in an incandescent bulb and I would think that should take care of the issue. Otherwise check your slip rings they might be slightly dirty too. Everything on that charging system is fresh.

Offline yamaguzzi

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Re: T3 charging question
« Reply #5 on: December 03, 2021, 07:02:18 AM »
I hard wired a 0-20 volt meter across the battery and mounted it on the bars.I can see exactly what my charging system is putting out under all riding conditions now.At idle it's around 12.3 or so by the time I'm in 2nd gear it's up to between 13.9 to 14.3 depending on how hard I'm riding.It runs between 13.9 and 14.3 at all speeds .This is way better than an idiot light and cost under 20 dollars to do.

Online Tkelly

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Re: T3 charging question
« Reply #6 on: December 03, 2021, 07:48:56 AM »
Thanks everyone.Apparently the issue is the type of bulb,not the system.Ican live with that but it seemed odd.

Offline n3303j

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Re: T3 charging question
« Reply #7 on: December 03, 2021, 08:47:17 AM »
Thanks everyone.Apparently the issue is the type of bulb,not the system.Ican live with that but it seemed odd.
It's not odd. The bulb is a resistive conductor in a circuit that supplies current to the alternator rotor through the brushes at start of rotation. The current turns the rotor into a spinning magnet that induces a current into the field, which is fed through the regulator and rectifier to feed the battery circuit. A portion of this generated current is fed back to the rotor to strengthen its magnetic field and in turn increase the alternator field output. The regulator monitors alternator field output and varies the current fed to the rotor to keep alternator field output in the proper range.

If the indicator bulb doesn't pass enough current to the rotor then the weak rotor magnetic field will not prkduce enough generated current tk feed back to the rotor to produce full output. LEDs pass very little current. There are many articles detailing what resistor to put in parallel with an LED indicator lamp to properly charge the rotor. Personally I prefer using the standard bulb to accomplish the task. I've lost 1 in 100K miles (and swapped it with one if it's mates to finish the trip).
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Online Tkelly

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Re: T3 charging question
« Reply #8 on: December 03, 2021, 08:58:28 AM »
So I should definitely change the bulb ?

Offline n3303j

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Re: T3 charging question
« Reply #9 on: December 03, 2021, 08:59:46 AM »
That's the easiest way. Just have a spare.
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Online czakky82

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Re: T3 charging question
« Reply #10 on: December 03, 2021, 09:02:42 AM »
Youíll have to remove the resistor too.

Online Kiwi_Roy

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Re: T3 charging question
« Reply #11 on: December 03, 2021, 10:06:14 AM »
I installed all LEDs in my Convert, now I can see the idiot lights in daylight but of course the LED doesn't pass nearly enough current to excite the rotor.
I just used one of the old lamp holders in parallel with the charging LED and dropped it into the bottom of the dash so I have the best of both worlds.
Actually I used 2 of the old lamps in parallel, I believe it now starts charging at lower revs (low reving Convert)
You could also use a larger bulb like a tail-light. I would keep the LED they are much more visible in daylight.
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Moto Guzzi - making electricians out of riders since March 15 1921

Online Tkelly

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Re: T3 charging question
« Reply #12 on: December 03, 2021, 10:31:42 AM »
To make an electrician out of me ,Roy,I would have to show up at your shop and spend a few months.My knowledge of electrics is that it is magic and when the bike quits the magic is gone.My mechanic knowledge is slightly higher..In my defense I am a pretty goodtrip navigator and I still can ride.

Offline lucian

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Re: T3 charging question
« Reply #13 on: December 03, 2021, 11:22:53 AM »
If it iant broke why fix it?

Online mtiberio

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Re: T3 charging question
« Reply #14 on: December 05, 2021, 06:08:01 AM »
check brushes
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Online Tkelly

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Re: T3 charging question
« Reply #15 on: December 05, 2021, 08:23:24 AM »
Iím going to try going back to stock,will report back.

 


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