Alternator

Thread Starter

way2afroz

Joined Dec 23, 2008
22
hello dear all,

i have a problem in the alternator?
when i give supply to "IG" terminal before the alternator is statring i get a supply in light terminal "L".

i must get the supply in "L" terminal when alternator is working and speed is 1500rpm as give in circuit


what could be tghe problem in the alternator?

regards
Afroz
 

bwilliams60

Joined Nov 18, 2012
1,198
Not sure I understand the question. You need 12.6vdc at ign terminal as well as on the "l" terminal on startup. When voltage is equal on both sides of the lamp, it goes out. What is the problem you are having. Better yet, do you have year, make, model of the car or what type of alternator you have, ie: bosch, nippondenso etc.
 

MikeML

Joined Oct 2, 2009
5,444
The idiot lamp backfeed to the field (to bootstrap the alternator; the old Motorola patent) hasn't been used in cars (exept in Russia) for more than twenty years... Modern alternators (the ones with the regulator built-in) use the Ign input as a control signal (from the ECU or the ignition switch) to tell the regulator to excite the field. The field current comes from the battery lead; not through the Ign wire... Regulation is achieved by the regulator changing the duty cycle of the field current (i.e. PWM).
 

bwilliams60

Joined Nov 18, 2012
1,198
The idiot lamp backfeed to the field (to bootstrap the alternator; the old Motorola patent) hasn't been used in cars (exept in Russia) for more than twenty years... Modern alternators (the ones with the regulator built-in) use the Ign input as a control signal (from the ECU or the ignition switch) to tell the regulator to excite the field. The field current comes from the battery lead; not through the Ign wire... Regulation is achieved by the regulator changing the duty cycle of the field current (i.e. PWM).
Not all true Mike. I was a rebuilder of alternators for many years and Nippondenso, Ford and Delphi used both Ignition terminals and Lamps terminals for many years and although I have been away from it for a bit, they may still be using that same configuration. Most manufacturers are using ECM controlled regulators now and the field is not controlled from the main battery lead but from a "sensing" lead from battery to regulator. This is a small 14-16 gauge wire which delivers battery voltage to the regulator. I still would like to know what he is working on because I am sure we can figure out his problem quite readily.
 

MikeML

Joined Oct 2, 2009
5,444
None of the cars, trucks, tractors, boats, airplanes, I have owned in the last twenty years have used an idiot lamp, let alone used it to bootstrap the alternator. These all have ammeters and or voltmeters, but no idiot lamp...
 

shortbus

Joined Sep 30, 2009
7,080
None of the cars, trucks, tractors, boats, airplanes, I have owned in the last twenty years have used an idiot lamp, let alone used it to bootstrap the alternator. These all have ammeters and or voltmeters, but no idiot lamp...
I can't speak for all makes, but GM as late as 2004(last new car I've driven) still has an idiot light(it's a led now), even with a volt meter. Don't believe it, turn your key to the "on" position and see it. :) And it's the amp meter that has gone the way of the Dodo.
 

gerty

Joined Aug 30, 2007
1,267
None of the cars, trucks, tractors, boats, airplanes, I have owned in the last twenty years have used an idiot lamp, let alone used it to bootstrap the alternator. These all have ammeters and or voltmeters, but no idiot lamp...
My 1998 Chevy pick up has a voltmeter, my 2010 GMC has a red light in the shape of a battery, no volt/amp meter.

Edit: The same (2010) truck will tell me how much air pressure is in each tire, and the % of oil life left, but not the oil pressure. I would think the pressure reading would be more useful than the fact that in 3,00 miles you need to change it.
 

Thread Starter

way2afroz

Joined Dec 23, 2008
22
Hello friends,
i am sorry to Reply late

i have Kubota Engine alternator


i have a problem in the alternator?
when i give supply to "IG" terminal before the alternator is statring i get a supply in light terminal "L".

i must get the supply in "L" terminal when alternator is working and speed is 1500rpm as give in circuit


what could be the problem in the alternator?
 

MikeML

Joined Oct 2, 2009
5,444
I cant read the terminal names at the back of the alternator shown in your diagrams. I see four: B (the big wire connected to the battery positive), and three others, I call top, mid and bot. bot has no connections in either diagram.

These are the minimum conditions to use this alternator to produce ~14Vdc output outside of its original application:

1. You must spin the shaft at least 1500rpm. When driven with a belt by an engine, this alternator has a much smaller pulley than the one on the engine, so when the engine is idling (say 900rpm), the alternator is spinning at least twice that fast(>1800rpm). A typical speed up in automotive applications is 2.5:1.

2. A 12V lead-acid (sealed or flooded) battery must be present. The battery provides the initial field current to bootstrap the alternator, and it acts as a giant filter capacitor for the alternator ripple. The system MUST have the battery... Connect the B terminal through a 40A fuse to battery positive pole (bat+). Make sure the battery negative is grounded to the frame of the alternator.

3. Connect bat+ first through a 5A fuse, then through a simple on/off toggle (field) switch to top. Turn on the switch after the alternator is spinning. If the alternator is not spinning, turn off the switch to prevent the battery from discharging into the alternator voltage regulator. If you leave the switch on, the battery will go dead in a day or so.

4. Try the connections above, spin up the alternator > 1500rpm, turn on the field switch, and check the voltage at bat+. The battery resting voltage prior to start will be <13.3V. If the alternator is charging, the voltage at bat+ will be >14V. If this is happening, you do not need to hook up the lamp as below.

5. If no charging in step 4, then proceed with this: Connect a 12V 4W lamp between mid and top. Try spinning the alternator again with the switch closed. See if you now have >14V at +12V.

My expectation is that you will not have to hook up the lamp. I expect that the lamp is there only as an indicator; it is not required to make the alternator produce output.
 

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bwilliams60

Joined Nov 18, 2012
1,198
Can you provide a picture of the actual alternator? I suspect that this will be a Nippondensor alternator or Hitachi. Provide a picture of the back of the alternator showing the connections please.
 

a211391

Joined Aug 6, 2019
2
The idiot lamp backfeed to the field (to bootstrap the alternator; the old Motorola patent) hasn't been used in cars (exept in Russia) for more than twenty years... Modern alternators (the ones with the regulator built-in) use the Ign input as a control signal (from the ECU or the ignition switch) to tell the regulator to excite the field. The field current comes from the battery lead; not through the Ign wire... Regulation is achieved by the regulator changing the duty cycle of the field current (i.e. PWM).
Hi. I just found the topic and it is quie interesting for me as I am investigating it.
As I understood you, you mean there is not idiot lamp on modern alternators where Ign input as a control signal (from the ECU or the ignition switch) to tell the regulator to excite the field.
But below you can see simultaniusly modern regulator and idiot lamp. What do you think?
upload_2019-8-7_10-19-29.png
 
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