Hi there
Couple of checks to help get to the bottom of why the fan (and which...) are running constantly.
Firstly, does the fan run constantly when the aircon is on?
If it does, is it just the large fan running?
If the small one isn't running (with the engine cold and turned off!) can you spin the blades by hand?
If the answer is yes to the first two questions you are looking at a probable issue with the small fan. The last question will indicate if it is seized or (as was the case with mine) one of the brushes on the motor has stuck in the retracted position. If it points to being seized its going to need swapping out. If it's likely a stuck brush then with care you can open and free off.
Hope this helps.