Should be on or off. There is no in between setting. I would suspect the level sensor is kaput. They do fail from time to time. Disconnect the plug, light should be off. Short the contacts in the plug, light should be on. If the glow disappears when you disconnect the plug, then it's your level sensor. if you need one, get it here, about $21.00 (cheap)

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.