2GM20F: Alternator question
- Thread starter Ken13559
- Start date
The AO should go directly to the battery. It should be fused at the battery end. An I/O switch is an option to allow servicing the alternator. There should NOT be a "T" in that wire.
Don't reinvent the wheel.
Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html
This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615
Don't reinvent the wheel.
Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html
This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615
The Wiring Is What It Is ........................
Follow the red wire from terminal B on the alternator up to where it meets the first "T". It then heads left and up to the "battery switch" and then to the battery. The "battery switch" must remain closed at all times while the engine is running. It can't be opened even for a split second. That's when the damage to the alternator diodes occurs.
Follow the red wire to the right from where it reached the previous "T". It goes to the "key switch"and from there down to the engine alarms. If the key switch is opened, all of your audible and visible engine alarms are turned off.
Is that smoke coming from engine down below
:cussing:.
............ but it won't damage the alternator if you shut off the ignition key.
Follow the red wire from terminal B on the alternator up to where it meets the first "T". It then heads left and up to the "battery switch" and then to the battery. The "battery switch" must remain closed at all times while the engine is running. It can't be opened even for a split second. That's when the damage to the alternator diodes occurs.
Follow the red wire to the right from where it reached the previous "T". It goes to the "key switch"and from there down to the engine alarms. If the key switch is opened, all of your audible and visible engine alarms are turned off.
Is that smoke coming from engine down below
:cussing:.Attachments
Ralph, thanks for confirming that turning Key switch off would not kill the alternator. Yes indeed the Battery switch must never be touch when engine is running.
Another question, notwithstanding other means of measurement, would having the Charging Lamp goes off upon starting the engine confirms the alternator is working?
Another question, notwithstanding other means of measurement, would having the Charging Lamp goes off upon starting the engine confirms the alternator is working?
You've got me there Ken.
The charging lamp, according to the drawing, has a + connection to the battery and completes the circuit back to the "L" connection on the alternator.
I'll have to defer to those with a better understanding of alternators to explain how the charging lamp works in your diagram.
Ken, the easiest way to confirm your alternator is working is to place a voltmeter across the battery terminals. This could be done at any 12V power point on the boat that is connected to the battery being charged (i.e. house or start).
The voltage should increase as soon as the engine starts, jump from say 12.8V to 13.5V after the engine starts to indicate current is flowing into the battery. The actual voltages you measure will depend on the state of charge of your battery and output current from the alternator. An increase in voltage is a sure indicator that the alternator has some output.
The alt light bulb gets 12 volts from the key switch and supplies that to the alternator. With no output from the alternator this alt bulb terminal is at ground so the bulb lights up. When alternator starts to spin up and begins to produce voltage the alt bulb terminal voltage goes up. So voltage "across" the bulb goes down until it goes out. If the alt output voltage is very low the bulb may glow or flicker.
hope that helps, Bob
The voltage should increase as soon as the engine starts, jump from say 12.8V to 13.5V after the engine starts to indicate current is flowing into the battery. The actual voltages you measure will depend on the state of charge of your battery and output current from the alternator. An increase in voltage is a sure indicator that the alternator has some output.
The alt light bulb gets 12 volts from the key switch and supplies that to the alternator. With no output from the alternator this alt bulb terminal is at ground so the bulb lights up. When alternator starts to spin up and begins to produce voltage the alt bulb terminal voltage goes up. So voltage "across" the bulb goes down until it goes out. If the alt output voltage is very low the bulb may glow or flicker.
hope that helps, Bob
Bob, thanks for the explanation. Question still remains, will the Alternator be damage if the Key Switch is turned off while engine is running? From what I understand, it should not as the Key Switch provides the field coil with exciting voltage to get the Alternator going. Thereafter, the field coil voltage is no longer required as the Alternator generates its own field. I haven't measure the battery when running the engine but rely on the LinkLite to tell me the charging current and voltage. So far not good. It seems to suggest Alternator isn't charging as there's no difference in voltage (12.6V) and charging current (-6A with fridge or +0.0~0.5A without)(I wonder why +0.5A).
When I get to the boat coming weekend, I'll drain the battery some and measure the voltage with DVM with & without engine running.
All there is so coincidence as I mistakenly switched off the Key Switch while engine is running. Another observation, at about same time, my new Ultrasonic Anti-foul blew its 3A fuse. Coincidence?
When I get to the boat coming weekend, I'll drain the battery some and measure the voltage with DVM with & without engine running.
All there is so coincidence as I mistakenly switched off the Key Switch while engine is running. Another observation, at about same time, my new Ultrasonic Anti-foul blew its 3A fuse. Coincidence?