Neutral light troubleshooting

[scott s]

I can't figure out why the neutral light won't work. Wiring harness and engine are 2000 GSX750F; dash is Bandit 400.

-checked the bulb and it's good.
-12V at blue wire coming from the neutral switch on the engine case.
-12V at the connector on the main harness
-12V at the other side of that connector, on the connector going to the dash

The manual says that the neutral switch is part if the safety circuit. I have the side stand switch bypassed (wires twisted & soldered together, then shrink wrapped) and the engine starts and runs and I can ride the bike, so I don't think that's it.

The clutch safety switch is present and functional.

It mentions diodes in the relay, but I installed a brand new electronic relay to slow down the LED blinkers. Plus, it didn't work with the old, stock relay either. If I unplug the relay, the turn signals don't work, as you'd expect.

Checked the 15A fuse for signals and it's good.

It mentions the ignitor box but, again, bike starts and runs just fine. There's a two pin connector that goes from the neutral switch on the engine to the ignitor box and it's connected.

I have 12V on the wire to the bulb whether the bike is in neutral or in gear. Is that correct?
I'm wondering if one of the wires coming from the switch (underneath the sprocket cover) is possibly grounded? I haven't checked that yet.
That only leaves a bad neutral switch, but would I still be getting 12V on that wire coming from the switch if it was bad?

 

[Tim]

Can you do a simple continuity test on the neutral switch? It should ground I think when in neutral, completing the circuit, so there should be no continuity from the wire coming from the switch to the engine casing when in first, but continuity when in neutral. Or the other way around.

I'm assuming the engine is grounded - you could check that too.

 

[scott s]

I guess you do that coming from the single (BLUE in Suzuki land) wire coming from the switch to the harness? The one that goes to the bulb in the dash?

If the neutral switch is sort of a sealed unit that goes into the crankcase, how do I check continuity if I can't really get to the other end? Or maybe I'm just not following you.

 

[Tim]

I think bottom line is if you get 12v from the switch regardless of bike in gear or neutral, it suggests the switch is bad.

Looking at images of the neutral switch - is it some sort of crazy magnetic sensor?

 

[scott s]

I'm not sure. I'd have to research that.

 

[pidjones]

Honda neural switches just ground the line. I would imagine most others to be the same. If it only has one wire to the switch that would certainly be the case.

 

[scott s]

OK, so I grounded the loom side to the frame and the light illuminates.

I'll pull the sprocket cover soon and see if I pinched/broke a wire. If not, I'll get a new switch and replace it on the first oil change.

 

[Redbird]

Before purchasing a new switch, try cleaning the contact point on it first. They'll sometimes get corroded or gummed up, especially if the bike had been sitting/stored for a while. And you should be able to pull that switch without losing much, if any, oil. They're usually located at the end of the shifter pawl (upper part of the transmission) and not below the oil level.