It's the other way around I believe. When one or both fans don't work the condenser get's no air through it and so it's high pressure rises to above 300psi really quick(seconds) and disengages the A/C clutch.Is your aircon working? Low refrigerant pressure can lock out both fans. I'm not sure if you have seen this http://pics.tdiclub.com/data/516/A4_Coolant_Fan_testing_Rev_7.pdf. It might be worth scanning the car and look for an error code on your A/C switch. Could be intermittent.