86560SEL, there are several potential causes for the low coolant light: 1) coolant level is low due to a leak in the cooling system, 2) a bad low level coolant switch that needs replacement. After you add coolant check the level in the expansion tank regularly to see if you're losing coolant. If so, it could be a worn out water pump, leaking hose connections, slightly blown head gasket, etc. If the coolant level stays constant and the low level coolant light comes on then it's likely the switch is bad.

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Fred Hoelzle