Nissan Repair: overheating when ac is on, nissan sentra, start the car

Question
my 1995 nissan sentra is overheating when ac is on. I've checked the fan if it is running and it does when i turn on the ac. Ive already replaced the radiator and the thermostat. What else could be the problem. I hope you could help me. Thanks in advance.

Answer
Don,

I bet the fan is not coming on with the airconditioner.  Start the car and let it warm up to operating temperature.  Now, open the hood and look at the one fan running.  Now, turn the airconditioner on and see if the backup fan comes on.  If it does not I bet that fan needs to be replaced.