I have and 05 STS 3.6 with 169K Miles. Sufficed to say the car was not well maintained by the previous owner. Bought it a few weeks ago at auction. Had a Bad Floor shifter and the Cooling Fans were pretty much burnt up with the motors falling out the assembly. Replaced the Cooling Fan Assembly with a used part. Fans Worked at the repair shop for a day of two then one of the motors seized up. Junkyard gave me a working replacement. Installed the replacement assembly and the fans won't kick on when the car gets up to temp and subsequently the car gets warm and starts to overheat.

Things we have Checked-Fans will not kick on even when running the A/C. Fans WILL turn on when jumped from the relay. Unplugged the Coolant Temp Sensor...no change. Changed the Thermostat...no change. Swapped the coolant fan relay...no change. Checked the water pump, Coolant seems to be circulating properly. Looked for signs of bad/worn wiring in the Coolant Fan harness.

What are we(myself and the mechanic) missing? Do the Coolant Fans in the 05 + STS have a module? If so, does anyone know the part#? Could the first junkyard coolant fan assembly that seized up, possibly have fried the module or a computer? Please remember the fans that came with the car were sooooo bad, that the wiring was fried and the motors had actually fallen out the back of the fan assembly.

My next step is to run the codes and look for anything relating to the fans. If that doesn't yield anything, send it to a Cadillac Repair shop to pinpoint the issue. Anymore tests that I can run or step by step diagnosing I can do before I send it to the pros?? Could this be a more serious electrical issue? Any help you guys can lend is greatly appreciated. I did some reading, not much out here with the 05 + STS relating to the cooling fans. My general mechanic is stumped.