Golf IV R32 :: CEL Code P2181 - Radiator Fans Do Not Turn On

So this seems to be a common code that is thrown when you near 100k miles, I'm at 77k .. This thread seems to be the most organized [URL] ....

"Long story short, there are 5 main reasons this problem can pop up, listed in order of likelihood, least to greatest:

1) Coolant sensor

2) Thermostat

3) Bad fans

4) Coolant mixture

5) Water pump "

My issue is that the only ones I'm (probably) able to rule out is coolant mixture and bad fans. My radiator fans do turn on from time to time, so I thought I'd ruled that out (unless it would throw a code for not turning on at appropriate times?)

I heard of a test to turn on your AC and see if they turn on, but my AC hasn't blown cold air like ever, so I don't know if that affects the test (probably not?)

A couple years ago I had a shop replace the original thermostat with the new one, or was it the coolant sensor, or both (ugh, I don't remember!) That leaves thermostat, coolant sensor, and water pump.

I guess my main question is is there anyway to find out which it is between these 3, without spending so time, money, parts etc? It doesn't seem the coolant sensor is easily accessible for one.

My car has been really slow recently but I also need to change the spark plugs, I'm doing that this week. I cleared the CEL/P2181 code and it returned a few weeks later,

I'm starting to change my mind about this car being easy to maintain/reliable, I'm always on time with maintenance and with only 77k miles on a 2004 car.