Good chance it's the Ballast Resistor.
Both Fans operate simultaneously whenever the DME calls for it, never singly or at different speeds.
The default whenever the AC is operating (compressor turning) is high speed.
Low speed is determined by the DME using a number of variables, there is not a simple set operating parameter. Coolant temp, RPM, Speed, even ambient temp all play a part in the DME determining low speed operation.
The relays, located in the driver kickpanel are as follows:
- #19 - left low speed
#20 - right low speed
#21 - left high speed
#22 - right high speed