The light in my rpm gauge remains on even with the ATV off and the key removed. I replaced the left light and headlight and I cleaned all connectors, applied die-electric grease then reconnected everything and all lights work, low and high, the ignition also works but I can't get the rpm light to shut off unless I unplug it from the harness.

Could it be a bad connection or wrong connection?

There is a black wire that comes out of the gauge into a gray plastic harness connector and if i unplug that single black wire the light shuts off.

Any suggestions much appreciated.

 

Out of your key switch you have a brown and a white wire, they both go in to red wires, one from the harness and one from the tach. Try switching these two wires and your light should go out.
You don't say what year model you have or whether or not it is a Baja edition. These tachs were for the the Baja but a lot of us did the mod so that wwe could have them on all models. Somehow the instructions that came with the tachs only worked on the earlier black models and the Baja's.
Hope this helps. Let us know if not.

 

Yes it's a 2003 DS650 Baja, I will test that out thanks for the info.

 

OK, so I tried swapping the red & brown wires that connect to two red wires one of which has a purple stripe and still the light remained on. I also tried it with both the red and brown wires fully disconnected and the light still did not go out. Only after disconnecting the black wire coming out of the RPM did the light turn off.

 

I know your trying to get it right before total forfeiture, but honestly I would have just unplugged it by now,no worries.