Generator Cutout Problem?

WOK · Apr 25, 2015

On a 42 H with orginal generator and cutout: With the switch high charge setting the generator (been checked out) puts out 12 amps when cutout is manually closed (stays closed) at higher engine speed then back to idle speed it discharges 4 amp for 10-15 seconds the to 0. At normal (low) switch seet no charging at any engine speed and a discharge with lights on. Is my problem the cutout or in light switch? What pulls the cutout points closed when starting up the engine?
I've an A that works so I may try switching the cutouts.
Thanks

Bob M · Apr 25, 2015

Sounds like the cutout is bad; probably also the charge control resistor on the back of the light switch.

A properly working cutout relay will pull in as the engine RPMs rise bit over idle. And the relay should drop within after a second or two after the engine drops back to idle. Also, at governed RPM the ammeter should indicate 2 - 3 amps with the light switch set on "L"

My advice: Ditch the cutout and replace it with a voltage regulator. A VR does a much better job controlling system charging operation which helps provide longer battery life.

Jim Becker · Apr 25, 2015

Bob M is likely right. But the first thing that came to mind as I read your question was a bad ground for the cut-out.

Owen Aaland · Apr 26, 2015

As for what pulls the contacts closed, there is an electrical coil connected to the armature terminal from the generator. As the engine speed up the output of the generator rises until the electric magnetic force is great enough to pull the points closed. The current flowing through the closed points also adds to the magnetic force keeping the points closed. As long as the voltage remains high enough the points will stay closed. When the engine speed drops the generator voltage output drops until it is low where the current flow through the points is reversed. This current flow creates a magnetic force opposite the magnetic force force created by the pull in winding. The magnetic forces cancel each other out and the spring pulls the points open.

Pitted contacts can cause them to stick closed and not open as soon as they should. It their condition gets bad enough and the spring is not able to open them, the contacts will stay closed even when the engine stops.

gene bender · Apr 26, 2015

I would get the generator serviced cause it is what make the voltages and current not the cut-out cause it sounds like the cut-out is working. I have 6 tractors working with the cut-outs and have found if the gen is up to par the cut-out works just fine.

WOK · Apr 26, 2015

Thanks for your suggestions and comentents. The generator was rebilt and checked out. Most likely the cutout ground may be the problem. I've adjusted the cutout down to a weak spring too and it stays closed at higher tension too after I manually close it.

gene bender · Apr 26, 2015

When voltage from gen falls off the relay should open. I takes6 pluss volts to close the points and they will open when volts fall back.

Owen Aaland · Apr 27, 2015

Cutout relay number 46412D (Delco number 1116766).
Spec number 602
Nominal air gap at core with points closed .020"
Nominal point opening .022"
Closing voltage range 6.4 - 7.8 volts.

Generator Cutout Problem?

WOK

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Bob M

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Jim Becker

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Owen Aaland

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gene bender

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WOK

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gene bender

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Owen Aaland

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