Chrysler Repair: Cavalier 99 cooling fan wont start, chevrolet vehicle, haynes manual

Question
The cooling fan wasn't working so I went ahead and bought the temperature censor and replaced the old one. I also bought the cooling fan fuse and breaker and replaced those also. After doing this I let the car heat up and just as the temperature reached half way the fan started working. After this I went ahead and drained the old coolant and filled it up again (50% coolant / 50% water) and after doing this the cooling fan stopped working. In other words I only got to se the fan working once after replacing the fuse and the breaker. Any suggestions as to what my problem is?

Answer
Hi Hike,
If I am not mistaken the Cavalier is a Chevrolet vehicle about which I have no wiring diagrams or experience with its cooling system. But on general principles I would begin by rechecking the fuse and the circuit breaker (reset if it is not a self-resetting type). If those are o.k. you might try unpluging the fan connector closest to its motor and jumping 12V directly from the battery to verify that the fan is working. If that checks out, then I would consider the possibility that there is air trapped in the cooling system such that the sensor is not being bathed in coolant. If the sensor is located at a thermostat box or manifold that has a removable plug screwed into it,  I would drain off part of the coolant to bring it below the level of the box (having first run the engine briefly with the heater temp set to full hot so as to open the heater core passage), then open the plug in the thermostat box and refill the system until the level of coolant fills the box, then put the plug back in and refill the system the rest of the way. That is a technique that is used for Chrysler engines with that type of design. I don't know if it is relevant to a Chevrolet engine; there may be another technique designed to avoid an air bubble at the coolant sensor. If you don't have a manual you might want to buy a Haynes manual for the vehicle, which are typically accurate and complete enough for the do-it-yourselfer.
Roland