2GM20F Alternator
- Thread starter Ken13559
- Start date
No..
Not unless your key switch also interrupted the B+ alt output via a relay or something... Killing the key only cuts excite power or the regulator. This is the proper way to cut alternator power.... It is opening the B+/Output while under load that kills alts.
Ken
When we first had the boat I asked the wife to turn the engine off and she turned off the key. It took about a minute or two and I asked why she hadn't turned off the engine she said I did and pointed at the key. I too though that was the kiss of death for the alt. but it tested fine.
Next day we went over all of the boats systems.
Walter
When we first had the boat I asked the wife to turn the engine off and she turned off the key. It took about a minute or two and I asked why she hadn't turned off the engine she said I did and pointed at the key. I too though that was the kiss of death for the alt. but it tested fine.
Next day we went over all of the boats systems.
Walter
It should continue to run, if you are using a facett or solid state pump, the engine should be able to continue to draw fuel. Even if the pump failed in a restricted condition, the engine will run for a surprisingly long time before it ran out of fuel in the secondary filter and its own plumbing.
When I test fuel systems, I will close off the fuel at the primary strainer, and at the tank. Many engines will run for 10 minutes or more at idle and even 5 minutes at high power settings, before tripping a filter light, and 5 minutes more before gasping. The power loss is gradual and may not even be noticed until it chugs.
When I test fuel systems, I will close off the fuel at the primary strainer, and at the tank. Many engines will run for 10 minutes or more at idle and even 5 minutes at high power settings, before tripping a filter light, and 5 minutes more before gasping. The power loss is gradual and may not even be noticed until it chugs.
Not Clear on This One ....................
But that aside, in Ken's diagram, I have showed the first "T" from the alternator as point "A". From there it's either up to the battery or over to the "key switch". I don't follow how switching off the "key switch" can cut the excite power to the regulator ? ? ? This is not shown in the diagram.
As the alternator is always (more or less) attached to the battery, isn't the field coil always excited and ready to produce current when the alternator is rotated ?
.................. which is nothing new in electrical matters.
But that aside, in Ken's diagram, I have showed the first "T" from the alternator as point "A". From there it's either up to the battery or over to the "key switch". I don't follow how switching off the "key switch" can cut the excite power to the regulator ? ? ? This is not shown in the diagram.
As the alternator is always (more or less) attached to the battery, isn't the field coil always excited and ready to produce current when the alternator is rotated ?
Attachments
If the regulator isn't "energized", how would it "tell" the alternator to produce power, even if the B+ is connected directly to the battery bank?
Seems logical to me .................. where is it shown on the diagram ? I don't see anything coming from the key switch except power to the alarms. ? ? ?
look at the wire that goes to the charge lamp it goes back the the alt( L ) and is only connected to the 12v when the key switch is made up ....the charge lamp is the current that excites the alt to charge...some one correct me if i am wrong
The amount of current would be small but maybe just enough to get things started.
However, once the field windings are excited, I don't see how they are de-energized by shutting off the key switch.
if i am correct on this ...when you kill the power to the alt light via the key switch the alt stops sending charge power to the bat......in essence the light is the messenger to the alt ....but i am not sure how the alt would start up if the bulb failed to make the connection (read burned out)...maybe because the buzzer is still sounding
I can't see any connection back to the alternator leading from the buzzer.
At this point I can honestly say, without fear of contradiction, just don't know.
Maine Sail
It does not take much power to or from the regulator to power the excitation coil. If you remove power from the excitation coil (either by the regulator doing its job,) or the key switch removing power from the whole circuit, the alternator will cease to produce power. I believe the bulb is a parallel take off from the charging circuit. If it burns out, you should still be able to charge.
If you put a metal screwdriver near the hub of the alternator (motor off and key off) There should be no magnetic draw since the excitation voltage is not present. Turn the key on (don't start the motor), and the regulator will send power to the exciter coil and this in turn will set up a magnetic field (and thus pull the screwdriver toward the hub of the alternator.) That excitation coil only needs enough 12v power to establish a magnetic field and thus induce a current when spun in relation to another set of wires. The regulator will increase decrease the current applied to the excitation coil in response to system load/demand and thus increase the amperage being supplied by the alternator.
In fact, the above screwdriver test is a great way to check if an alternator problem is with the regulator circuitry. If it never develops a magnetic draw when battery voltage is applied to a stationary alternator, then it is impossible for it to produce power.
The Blue Black line in the diagram appears to be the one providing power to the regulator. Switch off the key, and the alt. stops making power, but keeps spinning, and when the magnetic field collapses, the power is discharged to the batteries, vice frying the alternator.
If you put a metal screwdriver near the hub of the alternator (motor off and key off) There should be no magnetic draw since the excitation voltage is not present. Turn the key on (don't start the motor), and the regulator will send power to the exciter coil and this in turn will set up a magnetic field (and thus pull the screwdriver toward the hub of the alternator.) That excitation coil only needs enough 12v power to establish a magnetic field and thus induce a current when spun in relation to another set of wires. The regulator will increase decrease the current applied to the excitation coil in response to system load/demand and thus increase the amperage being supplied by the alternator.
In fact, the above screwdriver test is a great way to check if an alternator problem is with the regulator circuitry. If it never develops a magnetic draw when battery voltage is applied to a stationary alternator, then it is impossible for it to produce power.
The Blue Black line in the diagram appears to be the one providing power to the regulator. Switch off the key, and the alt. stops making power, but keeps spinning, and when the magnetic field collapses, the power is discharged to the batteries, vice frying the alternator.
dparille, thanks for idea to test. I'll give it a short this weekend. BTW, yesterday I motor for couple of hours with fridge and electronics running, no charge was going to the batteries. Guess my alternator is problem. Will give it another check this weekend. Thanks.