Shot gunning parts at a problem via process of elimination is costly and not the correct way to fix it.
1. If you're unsure of your ability to tackle a problem or lack the fortitude to see it thru, I suggest you let someone else fix it.
2. If you come to a forum such as this in an attempt to fix it yourself and ask questions, at least give what is suggested a try, you may find that people know what they're talking about.
3. If neither of the above two items work for you, then why bother, just get a new car!
: )
It has been laid out here, ways to approach and potentially fix the issue. But maybe you need to understand what will cause the fans to turn on or off to begin with.
First, the thermostat will not help the fans turn on or off. It just opens and allows coolant to flow upon reaching a certain temperature. Your engine has a temperature sensor which tells the computer how hot/cool it is. When reaching a certain temperature the computer will tell the fans via relay to turn on or off. So... Seeing as the fans are electric and not belt driven, you need to trace the circuit as mentioned. You can trace it from the relay to the fan and check for continuity without voltage to ensure there's no break in the wiring, grounds as well. Then you can check when the engine is up to temp for the fans to be on and see if there is voltage as it should be. You could cheat and swap the fan relay with another and see if it is the relay malfunctioning, or jump it out as you said. If the wiring is good, the relay is good, the fans are good, then I would agree the PCM is potentially an issue. Lastly, you could just bypass fixing it at all and install a switch as mentioned and control the fans manually...
but go ahead, change the radiator... Seems you've got lots of free time and money on your hands!
good luck! Don't forget to let us now how it all turns out...
