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Discussion Starter #1
I have a 2002 400ex and my neutral light never worked. Until one day I bought a new Oem neutral switch and wire going to it. I also put some never-seize on the bulb because it had loose connections. Now the neutral light will stay on in every gear and I can’t figure out why. If anyone knows anything, any help is greatly appreciated.
 

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The neutral light has power whenever the key is on - it turns on when the light green wire is grounded - the neutral switch simply connects the light to ground to turn the light on - either there is a short in the light green wire to ground or the crap you put on the bulb is causing a short.
 

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Discussion Starter #3
The neutral light has power whenever the key is on - it turns on when the light green wire is grounded - the neutral switch simply connects the light to ground to turn the light on - either there is a short in the light green wire to ground or the crap you put on the bulb is causing a short.
Okay, how would I check for a short in the green wire? I will take the stuff off the bulb first though. Thank you
 

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Discussion Starter #6
Find out what you have to disconnect to get the light to turn off
Well I took that crap off the bulb and it still did the same thing. If I unplug the black wire, it’s turns off. If I unplug the light green wire, it turns off. So how would I find the short? Or is it somthing else?
 

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The black wire is the 12v power wire - the green wire is the ground wire - if you unplugged the green wire from the neutral switch, you have a bad neutral switch or switch operator inside the engine
 

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Discussion Starter #8
The black wire is the 12v power wire - the green wire is the ground wire - if you unplugged the green wire from the neutral switch, you have a bad neutral switch or switch operator inside the engine
I think the switch operator because the neutral switch is new oem. How would I fix that inside the motor?
 

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Complete engine disassembly if it's the operator - it will need a new shift drum

Here's how it works:
This is the neutral switch inside the transmission
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This the neutral switch operator; a pointy button on the end of the shift drum
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Thatr pointy button contacts the brass spring loaded plunger of the neutral switch
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When the pointy button contacts the brass plunger, the path to ground is completed turning on the neutral light - for the neutral light to stay on via the switch, the switch is either damaged and shorted to ground or has a conductive substance coating it - some anti-seize compounds will do this.

To check the operator, remove the neutral switch and see if the button is on the shift drum - it is rare (I've only seen it once) where the pointy button broke off and the neutral light would not come on at all - more frequently, I've see the switch damaged where the brass button was pushed sideways and was permanently shorted to the threaded body of the switch. If the button is there when the transmission is in neutral, install new neutral switch - insert it one turn at a time and check continuity to find where the point first makes contact with the button and turns the light on - with a new sealing washer (#12) it will typically not turn more than two full turns past where it makes contact with that pointy button. You might have top possibly have to use two sealing washers to adjust the depth of the switch.

4311
 

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Discussion Starter #10
okay, I will try it out when I change the oil. I’m assuming the oil will come out of the neutral switch hole?
 

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Discussion Starter #12
When I unplug the wire from the switch, the light still stays on. Does this still match what your saying is wrong?
 

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If the light stays on when you unplug the wire from the switch, there is a short in the green wire to ground - try to find where the wire is pinched or shorted to the frame or another wire
 

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Discussion Starter #14
I figured it out, it was getting grounded somewhere else. I cut this wire and it work so is this wire supposed to be connected somewhere else?
4312
 

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That is the neutral light switch going to the diode - I assess the diode has failed (shorted out) and that is what's keeping the neutral light on all the time, but the diode is supposed to have only two wires going to it - the light green from the neutral switch and and a yellow/green to the starter solenoid and the clutch switch. If the diode shorted out, unplugging it from the wires should make it work, but it will then only start in neutral - the diode it there so when the neutral light is not lit, pulling in the clutch will close a switch to provide a ground to the solenoid so it will start in gear.
 

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Discussion Starter #16
So if I replace the diode and put the wire back on it will work then? What is the yellow/ red wire that is going into the diode as well?
 
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