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I have a 1995 JD 345. Turn the key on and the starter turns the engine over. I had read just about every forum on all sorts of different "how to". It seemed everyone was different. I completely disassembled my 345. Took ALL the wires out of the harness and checked each and every one. NO melted wires, NO burned components on the Ignition Interlock Module.

The thing that I did notice was that, AFTER going to the NEC website ( company that mfg the relays on the board ) I saw a schematic for the MR301 relay, which is the relay that SHOULD close when you turn the ignition key to the START position. After I used my volt / ohm meter I found the relay to be PERMANENTLY closed ! The contacts melted together and allowed the 12 volts to pass right on through going right to the starter solenoid without ever having to turn the key to start.

NOW the trick is trying to find the EXACT NEC MR301- N60L relay to replace my bad one on the circuit board. I have looked at all the electronic websites but can not find one. Anyone have any idea where to find one ? These relays are approx. $10 - $ 15. Beats paying $ 150.00 for a new one. I purchased a used one and that had the same problem.

Thanks, AES.
 

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Hello AES,
I do not know if it is helpful or not, but my GX345 uses EP2-3N1ST relays. Someone on this forum said the GX345 interlock module is the replacement for the 345 module. These relays are available on mouser.com.
 

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NOW the trick is trying to find the EXACT NEC MR301- N60L relay to replace my bad one on the circuit board
Unless there is something special about those relays, you don't need to find an exact match as far as manufacturer and part number. All you need to be concerned with is form factor, contact ratings and coil voltages. The form factor is just the shape or style of the thing, the physical form of it basically. For contact ratings, the higher the current rating the better, and I'd imagine all of them have voltage ratings within the values expected on a tractor (10-15VDC). For the coil voltage, pay attention to not only the nominal voltage rating (what the coil will see most of the time when it is energized) but also the drop-out voltage which is the lowest voltage the coil can be supplied with while still holding in the contacts. This is important because during cranking, battery voltage will drop sharply and if you need that relay closed to be able to start the engine, then you'll want the relay coil to be able to deal with low voltage.

Look on the schematic for those NEC relays again, do you see a diode across the coil? If not, cool. If there is, try to find a replacement that has that diode. If that is impossible then you can just add one across it externally, assuming there is not one in the circuit already.

Also, it helps if you call up some of those electronics suppliers. They'll often be able to help you cross-reference components!
 
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