ok we have 4 fords at home and a excel

ba xr6t
ba xls ute
eb2 fairmont
ef fairmont

now if i drive the ba's i can strap them with the aircon on and the temp gauges dont move at all

the eb is the same it sits on n and dosent move

in my ef its all over the place sometimes it sits a-l them r-m then a-l i can dribble around the streets and it moves all the way up. i have a new radiator, thermostat, hoses, the fans work its full of water and holds pressure.

does anyone have any ideas. ohh and when the aircon compressor is pumping are the fans ment to be on high speed because they go on high for a while the just fall back to low is this normal???