Tractor Won't Shut Off

[jpbmass]

I have an IH 574 Gas tractor that runs great but recently developed a problem where it will not stop running when I turn off the key! It will, however, stop when I disconnect the electrical line to the fuel shut-off solenoid. I checked the ignition switch and that appears to be OK. Once the tractor has stopped, there appears to be no battery drain. I checked the voltage at the fuel shut-off solenoid with the ignition key in the run position and there is no voltage -- the solenoid appears to be getting it's power from the alternator rather than a switched battery supply. Does anybody have any idea what is happening and how to fix it???

 

[old]

If it has an idiot light in the alternator excite circuit sound like it has shorted out so the bulb no longer lights up so the alternator back feeds the ignition system

 

[jpbmass]

That's interesting. My idiot light had been disconnected for some time; I think this no shutoff problem occurred just after I re-connected the spade connector to the light. However, the no shut-off problem now persists whether or not the alternator idiot light is connected. Now that I have a place to look, will troubleshoot and let you know what I find. Thanks for the idea ----

 

[used red MN]

What is the year of your tractor or the serial number? The early ones had an external regulator alternator and later had a internal regulator. I will attach a link to the CNHI parts pages for you tractor.
CNHI 574 Electrical parts diagrams

 

[jpbmass]

IH 574 serial number 6572 which makes it a 1972. I think I may have discovered the problem -- the ignition switch has 3 positions (off, run, start) with three inputs (battery, ignition & Starter solenoid). When the switch is in the Off position, I THINK the ignition is supposed to be grounded. When I measure the ignition terminal in the off position, it is floating. I'm going to spring for a new switch and see if that solves the problem.

 

[Jim.ME]

Ignition switch Battery terminal receives constant battery voltage (input) from a source such as a wire from the battery stud on the solenoid.

The ignition switch supplies power (output) to energize the starter solenoid only when the key is turned to the start position.

When the key is in the run position it supplies power (output) to the ignition, fuel solenoid, gauges, and possibly some accessories. It also can supply an internally regulated alternator with excitation power through an indicator light, resistor, or diode. One of these should be in the circuit to prevent back feed from the alternator which would prevent the engine shutting down when the key is turned off.

Unless you have a magneto which has to be grounded out to shut it down, your ignition terminal on the ignition switch is not grounded. Distributors need power to work, simply removing the power shuts a distributor ignition down.

To me an incorrectly wired alternator seems to be the most likely problem from what you have posted.

 

[jpbmass]

The tractor was running fine last summer but developed the won't stop symptom this spring. Nothing has been changed or replaced so something must have shorted, opened or broken. I believe I have an internally regulated alternator -- is the anti-feedback diode in the alternator? Is there a way to test to see if this is working?

 

[charlieu]

(quoted from post at 23:27:59 04/25/21) The tractor was running fine last summer but developed the won't stop symptom this spring. Nothing has been changed or replaced so something must have shorted, opened or broken. I believe I have an internally regulated alternator -- is the anti-feedback diode in the alternator? Is there a way to test to see if this is working?

With the engine running shut off the ignition switch and then unplug the wiring harness from the alternator. If the engine stops there is a problem with the diode that is in the wiring harness (IIRC). If the harness plugs into the side of the case the regulator is built into the alternator.

 

[Jim.ME]

(quoted from post at 18:27:59 04/25/21) The tractor was running fine last summer but developed the won't stop symptom this spring. Nothing has been changed or replaced so something must have shorted, opened or broken. I believe I have an internally regulated alternator -- is the anti-feedback diode in the alternator? Is there a way to test to see if this is working?

The "anti-feedback" diode (if it has one) would be somewhere in the harness, not in the alternator. An indicator (idiot) light can be used instead of a diode, I believe you said your idiot light isn't working. Perhaps something internally there has shorter and made a path allowing back feed from the alternator.

Do the test as Charlie suggested, and post the results. Keep an open mind, don't think it has to be a diode, your system may not even have one. The problem could be in the indicator light or wires shorter together in the harness somewhere.

 

[rustred]

been so long since i have overhauled an alternator and tested the components , but there is a diode trio is inside the alternator. pull it apart and check it.

 

[jpbmass]

I started the tractor, turned the ignition switch to the OFF position (tractor continued running) and then disconnected the wiring harness from the alternator -- tractor immediately stopped. It looks like the alternator is feeding voltage back into the ignition circuit when the switch is off. Does this mean I need a new alternator or can the diode assembly within the alternator be fixed/replaced?? BTW,, the idiot light indicating a bad charging circuit has been disconnected and is totally out of the loop.

Thanks to everybody for providing so much insight about what is going on.

Jim

 

[wore out]

(quoted from post at 12:11:02 04/26/21) I started the tractor, turned the ignition switch to the OFF position (tractor continued running) and then disconnected the wiring harness from the alternator -- tractor immediately stopped. It looks like the alternator is feeding voltage back into the ignition circuit when the switch is off. Does this mean I need a new alternator or can the diode assembly within the alternator be fixed/replaced?? BTW,, the idiot light indicating a bad charging circuit has been disconnected and is totally out of the loop.

Thanks to everybody for providing so much insight about what is going on.

Jim

There's nothing wrong with your alternator.

Installing a resistor, a diode, or an "idiot light" in the wire to the #1 terminal on the alternator's regulator will solve your problem.

If you are not into wiring and want to do it the easy way you can buy a ready-made harness with a diode in it. You simply unplug the existing harness, plug it into then diode harness, then plug the diode harness into the alternator.

ebay auction #202553914581 is one source, if you have an auto-electrical shop in your area they would probably have one to sell you or an autoparts store with a knowledgeable counter person could probably come up with one, as well.

 

[wore out]

To be more clear, the alternator is fine, this issue is happening because the alternator light has been removed form the "excite" circuit.

Putting it back in the circuit to the #1 "excite" terminal would be an alternative to the diode or diode harness.

 

[jpbmass]

GREAT - sounds like a simple fix. I'm really grateful for all the experience and knowledge available in this forum; it really helps keep these old tractors operating.

 

[Jim.ME]

(quoted from post at 17:31:21 04/26/21) GREAT - sounds like a simple fix. I'm really grateful for all the experience and knowledge available in this forum; it really helps keep these old tractors operating.

To add to what you have; here is more detail of what each terminal of the alternator does and the wire it needs. This is guessing that this is what you have for an alternator based on what was happening. You need to figure out where the wire attached to the #1 terminal is presently run to and get it run through an [u:9c5826008f]incandescent[/u:9c5826008f] (not LED) indicator light, diode, or resistor.

 

[jpbmass]

Yes, this is my alternator. Thanks to all of the inputs I've received, I think I finally understand what's happening. I spent $10 and ordered the diode harness assembly which should fix the problem. I'll also try to trace the wiring to pin 1 to see how this was originally supposed to work -- will repost when/if I get more information. Thanks again, Jim

 

[Jim.ME]

Someone posted this link a while back. This site has may wiring diagrams. Your 574 gas will be in the one titled IH 54-74-84 Series. It does show it has a diode in the wire going to terminal 1, no charge indicator light in that circuit.

https://cngco.com/wiring_diagrams.html

 

[jpbmass]

SOLVED -- the diode assembly arrived today; this solved the problem. Thanks again to all who helped. Jim B