WOODY1982-1

i have a 2002 ghia 1.9tdi about a month ago my temp gauge started to go a bit loopy and was bouncing up and down so i changed the sensor on the right hand side at the back of the block and decided to change thermostat at the same time, all was well until climbing a hill ,working the engine, temp gauge will go up slowly until i back off the power then returns to normal, it has gone in to the red a few times but again once i let the strain of it went back to normal 90 within 20 seconds some info for you ive never seen the rad fans come on at all aircon is broken (broken pipe) but even when i select low on climate control no fans at all, so change sensor on passenger side of rad but still nothing the do come on when connected to battery and when i cross the wires to the switch( hence why i thought it was switch failure i can clearly see water returning through the return pipe at top of expansion tank and i bought a new cap for it and theres lots of pressure when i undo the cap and the water floods back into tank when the cap is released otherwise it looks empty until i release the pressure top radiator hose gets very hot in fact all pipes get hot except for the bottom hose going to the thermostat, this always feel very cold and so does the radiator i dont know what else to do, i was thinking maybe a relay or something, maybe fans arent being told to come on but i dunno any help would be appreciated dont want to scrap as i just put it through the mot