Should both fans spin at the same time in 99 maxima or does each of the two have different function?

Should both fans spin at the same time in 99 maxima or does each of the two have different function?
Both should spin at the same time, if your AC is on.
Otherwise, one will spin until the engine reaches a certain temp; then it will add in the 2nd fan for additional cooling if necessary.
Bottom line, if you turn on your AC, you should see both fans come on. Otherwise, start checking:
- Thermostat
- Fan relays (under the hood, near the battery, 2 of them)
- Electrical voltage to the fans themselves