Volkswagen Repair: 2003 jetta, green fuse, coolant temp

Question
I have a 2003 Jetta 1.8t that I have had for about 6 months. Recently the check engine light came on, i scanned it with an OBD II and it said there was a cooling problem. I went to the dealer and got a new heat sensor and replaced it. The check engine light turned off. A week later the light came back on and the OBD is still reading the same code for a cooling problem. i let my car idle for about 45 minutes to try to see if the cooling fan turned on. It never did, but my car never went over in temperature. any suggestions on what it might be?

Answer
There are a couple of heat sensors on your car. The fan switch sensor on the driver side bottom of the radiator and the sensor on the coolant flange driverside of the cylinder head. should be a black connecter and a green sensor. The sensor is the main reason for the fault to set. The best way to diagnose this is with the factory scantool. There are a few different cooling system fault the P0# would be helpful. The thermostats and water pumps come next. The thermostat sticks open allowing the warm up time to be longer.  The water pumps have the plastic impeller break on your engine causeing no flow. The next problem would have to be the cooling fans. You say that the fans are not working. The fans have a 30Amp fuse on top of the battery. This fuse when looking at the battery cover is under the cover and inside the pocket. The fuse should be green in color and will be on the left of the three green fuses. Check the green fuse. A easy way to see if the fans are working is to turn on the ac and see if the fans spin. Your fans have two speed high and low depending on coolant temp and the ac pressure your fans will operate at different speeds. If the fans do not turn on when the ac is on then you have a problem. The fans both sides may be bad or the fan  switch or the fuse is blown which if it is then the fans are bad anyway. Replace the fuse if blown and retest. Wiring problem of the fan control module. The only way to be for sure is to see what temperature the dtc set in. -40degrees Celsius or 300degrees is two separate things. You do not have this capability so you have to check one thing at a time. So check the fuse. Turn on the ac and check the fans. Make sure the orange ac light is on and the blower motor is blowing out air then check the fans. Let me know how it goes.