Ok, I finally had a few minutes to verify everything. In my '95 E320 wagon, the high speed fans are controlled by the GREEN relay with 30A fuse in slot C, which is closer to the front of the car. The low speed fans are controlled by the BLUE relay, now with a 20A fuse. This relay is in slot B, which is towards the rear in relation to the GREEN relay.

I verified the high speed relay by disconnecting the 4-prong thermo sensor which caused the fans to run at high speed, then I pulled the GREEN/30A relay and they stopped.

Thanks again for your help!