Weird fan problem...

i had the same problem last week. trust me it's your electonic coolant temparture sensor(ECT) . my fan would only come on when the A/C was on. before you buy the part check the plug that goes on the sensor to see if the wires are frayed. the part cost 16.99 from autozone. the ect is behide the top part of the upper radiator hose on the left side of the distributor. don't forget to get your teflon tape to put around the sensor's threads. one more thing, don't let them sell you a coolant temperature sending unit. that's used for your temperature gauge inside your car. the ECT is much larger.