Quote:
Originally Posted by C5rider
Then I shut it off. And it didn't! 
It kept idling (chug, chug, chug... ) |
Ah yes - say hello to your newest friend, the CUTOUT RELAY in the regulator.
The cutout relay contacts are normally open until the engine is running fast enough to run the SG at a speed which allows the SG to switch over from being a "starter" to becoming a "generator".
When the engine / SG running fast enough for the SG to generate approximately 10 volts or more output,
the CUTOUT relay windings are energized by the SG's 10 volt + output and the contacts of the cutout relay then CLOSE - allowing the SG generator power to flow thru the regulator to the battery.
Think of the cutout relay contacts as an electrical bridge between the battery and the generator.
Backing up half a step, when the SG is used as a starter, engine speed is low so the cutout relay is NOT energized and the bridge between the battery and SG is open. This is normal.
So let's say the engine doesn't start and you shut off the ignition switch. NORMALLY the cutout relay contacts are open (remember no SG output = cutout relay contacts open). If the cutout relay contacts are open (as they should be), there is no electrical connection between the battery and the SG at this time. Follow the black arrows below - the SG is disconnected from the battery by the open circuit at the cutout relay contacts).
Now let's say the cutout relay contacts are pitted and they happen to stick together (not normal operation). There is now an electrical bridge between the battery and the SG and the connection remains intact even tho the ignition switch is off -
battery power is now back-fed to the SG and allows the SG to become a starter again. Chug Chug Chug.
You are lucky the tractor was not in gear. I have seen tractors parked in sheds in gear walk out of the sheds by themselves if the cutout relay sticks.
And BTW, if you start messing with the regulator and accidentally close the cutout relay contacts with your fingers, the tractor will start to crank - and you won't be able to stop it until you open up one of the battery cables or physically separate the cutout relay contacts. Why?
Because when you close the cutout relay contacts by mistake and the sg becomes a starter, current thru the cutout relay windings is now high enough to energize the cutout relay and keep the contacts closed !!
Both of these are hard to do if you left your tractor in gear and you are now chasing it across your lawn into your neighbor's yard !!
Another point while we are discussing this - the "back- feed" path thru the cutout relay was not meant to handle the load of the SG starter current. Backfeeding the SG in this manner is harmful to the relay coils in the regulator unit. Extended "back feed" cranking can overheat and destroy the coil windings in the relays in the regulator unit. The starter current was meant to be bypassed around the regulator and handled thru the starter relay wiring (in green below).
and that is all your going to get at 3 in the morning. Let me know if you have questions.