I've got an old 96 Escort TD 1.8 with the Endura engine. I've noticed that as I turn the ignition and wait for the glow plugs to warm, my engine fan is kicking in straight away, even though the engine is stone cold. Is it supposed to do this or is it likely I've got a knackered temperature sensor or the previous owner has wired up the fan permanently?

Any rough estimates on how much to fix it?

Thanks

Matt