Today I was driving in traffic, looked down and my temp guage was on "H"
I pulled over, opened my bonnet and my fans were not on.

I checked my fuses, they were all ok, I checked my relays, they all work perfectly.
My fans work when I turn my A/C on, and also when I bypass the relay with a paper clip.
The temp guage goes up and down, up when I'm stopped, down when I move, but it also sometimes goes back up when I'm moving.
Eg, if it's at 9/10th when I'm stopped, I'll drive and it'll drop to 6/10th then go back up to 8/10th. (It doesn't go as high as when I'm stopped)

At first I thought it was the thermo fan switch, since the fans do work, relays and fuses are ok, but I'm unable to actually test that, since I'll need to unbolt and remove my radiator to get the switch out.
I'm not sure if normal 3rd gens are like that, but my Inx model has a bar across the top of the switch, so it can't be pulled.


Now I'm not sure if it is the thermo fan switch, since I went for a drive before, with my A/C turned on, which made both radiator fans stay on, yet I still overheated.

Do the radiator fans operate at a lower speed when the A/C is on, but the fan switch isn't activated?

 

Well I took the car out again, it's 8pm and the air is quite cool.

I went on the motorway, did a steady 60mph and the temp guage went past the red band, and I got off the motorway quick, while I was idling at a light, before I could park, the temp went down to about 3/4.

After a bit more driving I've discovered when I rev the engine, the temp goes down, but when I stay at a constant speed of driving it goes up, when I idle it goes down too.

This makes no sense to me, the coolant IS circulating, but it doesn't matter how much air goes through the radiator, it'll only go down when I idle, or rev it up.

So what I'm thinking is one of the following:

The water pump is stuffed, when I rev the engine, the water pump spins faster, pumping a bit more water, but still not enough.

The thermostat is stuffed, not opening up enough.