Noise Under Battery

I have a 2001 Ford Taurus. There is a box under the battery (sounds like a fan) that is running and will not cut off. What is it and how do I fix it?

Does it stop running when you disconnect the battery? What is it connected to? Look on a wiring diagram to see if it can be identified. Can you post a picture?

It does cut off when battery is unhooked. I left battery unhooked all night and it stopped. Was told it sounded like the ABS pump. It is a square metal box directly under battery.

Do you have a local Midas or some other brake shop that does free brake inspections?

You need to replace the $75 relay that controls the electric air pump for excess air to the catalyst. It is mounted to a bracket on the lower left front frame rail that also holds the air pump itself. Removing the bracket is a real PITA is lying on the garage floor...not so bad on a lift. Around 1 hour labor.

JVH