Alright I am completely stumped and need some help. So my car has started to overheat. My radiator fan won't kick on no matter how hot it gets. Now if i turn my a/c on, both fans will turn on, but that is the only way I can get either fan to turn on. Without them both on of course the car begins to overheat very quickly.
Now here is everything I have replaced trying to fix the problem, some of them were done before this issue even started, but it had always ran slightly hot and sometimes would begin to overheat but if i pulled over, turned the car off and then back on, everything was fine. But all replacements have been in the last week and the issue started two days ago.
1. 160 degree thermostat (never used anything other than the stock 192 before and wondering if this could be involved somehow??)
2. Temperature sending unit also called the temperature switch
3. Coolant Temperature Sensor
4. Cooling fan switch (both on the thermostat housing and the bottom of the radiator, the bottom of the radiator one I think is called like the thermo temp switch or something like that, but I was told they're the same sensor so I replaced both of them)
5. The radiator fan relay

Yet for some reason the fans will only kick on if a/c is on and even then it seems to run slightly hot. I have been looking and cannot see any leaking from my water pump.

I really really need some help on this one because I cannot figure it out for the life of me and I obviously cannot keep driving my car while its running hot.

I'm not sure exactly on DSM's, the rest of the guys here would know, but I'm guessing that the fan is controlled by the computer? Maybe double check your computer grounds and make sure one's not corroded. The other thing you can do on the cheap, as a temporary fix, is just wire a switch to your fan relay (manual turn on) and bypass the input from the computer/sensor. Not an ideal, but will get you by until you can figure out the signal problem.

Seems to me your changed everything that control the fan except for the ecu. You could try swapping the ecu's, if you could find one.
As dualdj1 suggested, check all you grounds as well as the connectors at the sensors. They can look ok, but the wires could be corroded.

I beleive the fans run all the time with the AC on, so it would be over riding the cooling fan switch.

Have you tried taking it to an autoparts store or if you have a logger, check it for codes.

Checked for codes, nothing is thrown. I have a 90 laser fwd rst ecu, and the car i am having the problem with is a 92 talon tsi fwd. If i'm not mistaken these ecu's dont match up do they?

also one more thing that might make it either seem like the ecu or some other issue. The temp gauge is registering hotter that what it should be possibly. It shows the car heating up to usual operating temp before the car is really warm at all, like i can take the radiator cap off and put my finger in the fluid and its just slightly warm when temp gauge is registering the car is where it used to be at op temp. A mechanic friend of mine said to him it sounds like the temp sending unit is grounded somewhere. Now that you've mentioned the ecu it sounds like that might also be the issue.

Well you're coolant won't be hot to the touch until the thermostat opens (generally). Temp sensor measures temp directly in the block before the thermostat. If the gauge shows cold before starting first thing, then it shouldn't be grounding out. May have a thermostat stuck closed. Turn your heater on to hot when the temp gauge says it's at temp. if you're heater is hot, and the antifreeze at the cap is still cold, I'd change therm. Still might not fix your fan prob though.