Good time to drain coolant and refill.Doing thermostat would be great .There is a red drain screw at the bottom of the radiator .Using long screwdriver turn screw but don't remove.drain ,tighten,refill.
If the coolant light glows when the bottle is not low then the switch at the coolant tank is going bad.cheap and easy
Good luck
Rich

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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car