I have a 94 k2500 gmc suburban with the 454 and a/c. I am having a problem with my heater fan motor. The motor works fine but only on low or high. There are two medium settings where nothing happens anymore. As i go though the differnt positions i can hear a soft clicking coming from what appears to be four relays sitting on top of the heater ac unit under the dash. I have the glove box out. How do i isolate the relay? Are they all the same part? Can anyone help me? I have read the available posts and feel like I am close to a solution.