I notice my driver side fan on my 03 I35 only goes on when the ac is on, when its off only the passanger side fan is on. Is this normal? Also yesterday I did a coolant flush beacause the temp would sometimes jump up high and go back to middle but today that does not happen.

 

That is not normal. The radiator fans should always run together as a pair.

What I don't understand why it runs when the a/c is on and not for regular, non a/c cooling. Would you double check something? When the engine is cold (like in the morning), start the car, turn on the a/c and look at the fans. I suspect it will not be running, but will come on later as the engine warms up. If this is what happens, you have a bad fan motor.

 

I turned it on for the first time in a few hours and drove around. Still the same.
No ac/ Drivers side fan off. Ac on Drivers side fan on. Passanger side always on

 

This just doesn't make any sense. The fans are turned on and off by the ECU, There is just one signal from the ECU, pin 35, that goes to both fans. How one fan will some how not get the signal sometimes is perplexing. UNLESS...

Maybe the problem is the passenger side fan isn't shutting off like it should and is on all the time. Again, check something. When the engine is cold, start the engine. But this time do not turn on the a/c. Look at the fans. Both fans should be off until the engine warms up.