WE have a fan constantly blowing over the coils

It is not normal if there is less traffic - in and out of the fridge or freezer - if all is ok.

At night it should run less. You have 1 condenser fan to service both freezer and fridge compressors, which run independent of each other though they both regulate the condenser fun.

If you you have a dirt condenser coil (on to of the appliance), the cooling effect reduces, causing the compressors run longer till the meet the cabinet set temperature. Every time a compressor runs, the condenser fun runs.

If you have less traffic and have a clean coil, then call a service tech.