I have a 2008 vue.
When you turn the key on one fan starts up and running. Keeping the car to take more time to heat up.
What can cause the fan to turn on to soon.

 

• Bad engine coolant temperature sensor
• Is AC accidentally engaged?

 

I haven't checked the AC yet but will.

 

How did you check the temperature sensor?

Also, the AC has a relay most likely in the underhood junction box. The AC will run only if this relay is closed. It is usually commanded by the BCM to close as appropriate. It is possible that the relay is stuck closed so even if the AC is not on, the relay may be stuck closed.

These are general comments not specific to a 2008 VUE.
​​​​​​Don't know which engine you have, trim level etc. Please add. Not that any of that would affect AC operation. There's a chance the AC relay is actually integrated into the BCM. I'm simply not sure.

 

Is the HVAC unit in defrost mode?

 

The front fans are both powered through relays as well in the underhood fuse box: https://fuse-box.info/saturn/saturn-...uses-and-relay

There are two relays according to that fusebox diagram, "Cooling Fan Main" and "Cooling Fan Aux". I would try just switching those two relays around and seeing what happens - if your other fan now becomes the problem one that turns on too early, then you will know you have a bum relay.

 

I had similar issue. 1 fan running at hi speed. I unplugged both fan connectors and cleaned them and reseated them and now both fan runs like expected. With lo and hi speeds.