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300 starter relay update

Z

Zachary Hoyt

Well-known Member
I got the new relay yesterday and put it on. Now it starts and the starter stays off except when I push the momentary switch, but when I shut the tractor off the first time it kept running. I found out that there is battery voltage to the I terminal at all times, and I had thought that it was only supposed to have power when the momentary switch was pushed. After I disconnected the wire from the I terminal the tractor engine stopped just fine. Did I get a new relay with a problem or have I misunderstood how it is supposed to work?
Zach
 
Some what I refer to as Ford type starter solenoids as well as some GM and some tractor solenoids have BOTH a small "S" terminal plus an extra "I" terminal. Normally S is the solenoids activation terminal which if voltage is applied the solenoid engages/closes and voltage is thus applied to the starter motor. Normally I is hot ONLY when the S is activated and its purpose is to feed battery voltage (i.e. by passes ballast resistor) to a 6 volt coil on a 12 volt tractor for a strong starting spark but its dead/open when shes not cranking.

If your solenoids I terminal is hot all the time theres a problem since on most its hot ONLY when the S is activarted and the starter motor is cranking.

You need to unhook the wire on the I terminal and use a meter or test lamp to see if I is actually hot ONLY when the solenopid is engaged orrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr if shes not wired right and that circuit (the wire you unhooked off I) is getting the wrong hot feed elsewehere???????????? that wire is usually hooked to the coil so the baLlast is by passed only while cranking.

John T
 
The wire on the small I terminal goes to the coil side of the voltage resistor. I checked it with a meter and found that even when the ignition switch was off there was still 12 volts at the I terminal. I disconnected the wire from the I terminal and now it shuts off when I turn the switch off.
Zach
 
Zach when the on off switch is on there will be after resister power to the I terminal. That power shouldn't pass through to the S terminal when the switch to energize the S terminal is not powered. Don't know if it matters the side battery cable goes on. Tractor I looked at is closest to the I side with no problems.
 
Thanks, that makes sense. I went out and checked it again and there is 12 volts at the I terminal even with the wire to the coil disconnected from it. I will try reversing the big terminals again so that the hot side is closer to the I terminal and see if that fixes it.
Zach
 
I pulled this image from a Ford diagram. It is correct. Feedback from the alternator could register there unless a diode is used. Best of luck, Jim.
c51153.jpg
 
I did put a diode in the line where it was shown on the wiring diagram, so I think it is correct. I am going to try swapping the leads and see what happens.
Zach
 
Don't think it will help. Shouldn't be voltage going from the relay switch to the I terminal unless the switch engages the starter.
If the tractor starts good without the wire from I to coil you could drop it.
Lots of H and M tractors are changed to 12 volts without the wire bypassing the resister.
 
I went ahead and switched the wires and now everything appears to be working as it should. I have no idea why, but it seems that way. With the battery voltage on the terminal next to the S terminal the I terminal had 12v at all times, with the wire switched to the I terminal side the I terminal does not have voltage when I check it. I am not able to keep a meter on it and press the start button at the same time so that will have to wait till there is someone here to help. I am mystified but as my old boss used to say "Don't argue with success."
Zach
 
Use another 4 amp diode. Place it in the wire going to the coil side of the resistor. Attach it so the band end is toward the coil. Attach the other end to that S terminal. Now the starter switching voltage will be the bypass supply. The diode prevents the ignition voltage from energizing the S terminal. Jim
 
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