On my 2001 olds silhouette I can't find a radiator fan control relay, its not located in the fuse box located under the hood. The part number is R4005Z, in an effort solve the problem; coolant fans not switching to high but only operate at a low speed with the A/C on or off. Checked all other relays and fuses "good", I also replaced the sensor located near thermostat. Can you help out with any other areas to troubleshoot before I replace the dual coolant fan unit?