95 Chevy MC low coolant warning; has plenty coolant

The "Low Coolant" warning light is on in my '95 Chevy Monte Carlo Z34, 90K miles. There's plenty of coolant in the radiator & reservoir. However, neither of the fans by the radiator are working. I replaced the relays for the primary & secondary cooling fans (nos. 16 & 17) but still no working fans. Temp. Gauge is fine and car hasn't overheated, knock on wood. What could be the problem? Thanks for any help!