I have been working on a similar issue. The passenger side fan is the sub-fan, the drivers side is the main fan. In order to check if the main fan is working, the best way is to jumper the fan. Unplug the connector to the fan. You will see three contact points. 1 is the ground, the black wire i believe, the other two are low and high speed fan operation. Run wires from the fan connector straight to the battery. If the fan operates, the fan is good. You could have a bad relay. The relays are located under the hood on the drivers side fuse box. The fuse box cover should show the relay locations. One fan, the sub fan I believe, operates when the AC is on, the other main fan is for standard cooling I believe.