auxiliary fans check--1998e300td

[ready-ronnie]

I was sitting in parking lot on a hot day, waiting for wife, with the air running and Temp goes up to mark passed 100. I figure its a good time to check to see if Aux, fans are running. Their not!! Should they be?. I have never seen or heard them run. Would this show up on computer read out? It never has. Does anyone know a simple check? Any help would be appreciated