Hello, does anyone know if both cooling fans should run at the same time. The ac cuts out at temp over 90 and I believe I might have a fan problem. Looks like only the driver side was running when I had the ac on and the engine was hot. It never shows high on the temp gauge. Thanks for any help, john
It's on an 11 fx50s by the way.

Usually, turning on the AC will turn on both fans. Anytime the secondary/AC fan (left side US) runs, the primary one (right side US) has to be running as well.

If the AC is not on, then the main radiator cooling fan will come on as needed - generally off while going at highway speeds, and on while idling.

As to why a fan isn't running, there are a few possibilities:
1. Cooling fan fuse/fusible link
2. Cooling fan relay
3. Fan control module
4. Mechanical failure of the fan assembly
Since you have a twin setup, you could troubleshoot #s 1-3 by switching the electrical components. #4 can be tested by safely (ignition off) spinning the fan by hand to see if it moves freely and sounds or feels normal compared to the other one.

Thank you very much. I tried swapping out the modules and couldn't get the rt passenger side fan to move even though it moved freely by hand. I ordered a fan assembly and should be changing it out this weekend. Thanks again for the operation sequence. I'll post back how things work out