Auto Air Conditioning & Heater Repair: Radiator (fans) not comming on, nissan sentra, radiator fans

Question
Paul;  Thanks in advance for your time.1999 Nissan Sentra 1.6 auto with air. Neither of my radiator fans are coming on. I replaced the relays and fuses. I've checked to make sure the fans are operable which they are. Recently replaced waterpump due to leakage. A/c blows cold air most all of the time. When sitting in traffic it seems to blow less than cold but still working.for sure the fans are not coming on. What else can I possibly check.
Thanks
Kam

Answer
Hello
It sounds as if you have been thorough.
We are a uk company so have no specialist knowledge of your vehicle.
How are the fans controlled ?.
Are they managed by the  ECU or temperature sensitive ?.
It is possible that a temperature sensor is at fault. You need to know whether it has one of these either in the fan assembly or somewhere round the radiator.
Is there power to the fans, if so it could be the fans themselves that have failed.
With the ignition on without the engine running find the feed wire and with a volt meter see what is being fed through. If it is dead feed 12 volts into the cable and see whether the fan runs.
You also have a high pressure switch on the a/c system. Audi for example have a problem with these and that too can prevent the fans from working.
I hope this gives you a bit to go on, contact me again if you would like some more help.