noted no coolant in overflow tank?

1995 Acura Integra LS 1.8L not VTEC mileage: 67,700. Noted for several months coolant temperature rising but never very high. Opened hood to change oil and noted no coolant in overflow tank. Fluid level in radiator low as well. After refill, fluid noted to be seeping out around seal between upper plastic part and metal body. Replaced with new radiator. After refilling and bleeding out air, noted fan wouldn't come on even when temp approaching straight up on gauge but would come on normally with a/c or if ECT switch shorted across. Replaced ECT switch but no change. Tested ECT switch that was pulled (after the fact!) and it worked normally. Tried running it and burping it to get any air away from the ECT switch but no change. Even tested the relay in the under the hood box. It works normally with and without power. Where to go from here?