Last week my wife’s ML320 had a service done at the dealership where they change the wiring harness for the auxiliary cooling fans. Their claim was the fuse blown for the aux. fans. She had never had a problem with the fans before that. However I remember those fans starting up for a few seconds after starting the engine with or without the A/C. After this replacement they start only and only when the A/C is on. I check them with the engine hot (92-93 Celsius measured at the thermostat housing) and they do not start unless you put the A/C on. Is this normal? At what engine temperature they should start?