W210 Auxiliary fans not working properly

[bfdiesel]

I am looking for some help in understanding an A/C problem I have with my E320 98 station wagon. A little over a year ago I paid quite a bit to have the A/C repaired. One of the items replaced was the dual auxiliary fans. I checked them by setting the climate control unit to test mode (key in position 2, depressed both Auto buttons 10+ seconds). Sometimes they turn on and sometimes I hear a humm and with a little spin help they will start. I have not seen them come on while the car is running. This could be the reason why my car cools at start but when faced in traffic it goes very hot. Any ideas to fix problem?