Cooling fan on 2001 Pontiac Montana

I've changed the thermostat,cooling fan relays and cooling temp sensor. But,still the cooling fans only works when the a/c is turn ON, otherwise it the temp. gauge goose higher than normal. What can possibly be the problem?

Asked by for the 2001 Pontiac Montana
It's a complicated system and I can't give you a good answer without inspecting the car myself.
Get it checked ASAP so you don't damage your engine by overheating.
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