Fan is running constantly

hey dude your problem is so simple..below are my solutions.
if you already secured the fans for the replacement then its easy for you to do it, try to totally shut down your UPS removing the input and battery supply. avoid replacing the fans with power, its to dangerous. it consist of almost 400VDC inside in it.
call me if you want +63923 3024 585

The charger in powerware 9 series 9120 6000i ,the fan is of a quality that it fails and the heat sink does not get sufficient cooling ,it runs on 12 volt ,i replaced it with a cpu fan from a mainboard on a pc and it works perfectly now. make sure that the fan is running else the charger might go in protection or can fail due to the transistor on heat sink fails.

No its not.
Both fans should run. You should consider replacing the fan.

The cooling fan is probably not working. Unit will overheat. Check the fan to see if it run continuously with no scraping noise with the UPS turned "ON". If the fan does not run, open the case and replace the fan.

A good electronics supplier should have. Get the correct voltage and size, and get one with the largest CFM available.

You're absolutely right, overtemp on batteries can greatly escalate the failure of batteries, particularly older or heavily loaded ones. The fans are a fairly easy replace, if we can assist in any way, please do not hesistate to contact us.

http://www.gowithon.com

On Services can assist you in the repair of this UPS fan and any other critical power service parts/repairs. We have nationwide service, please contact us if you are still looking for assistance.

http://www.gowithon.com

call powerware

You can download the manual and other literature at
http://www.powerware.com/EMEA/UPS/9120_info.asp

The contacts for support in India are found at
http://www.powerware.com/India/Service_Support/IN_Office_Contact.asp

They offer a battery monitoring software package, at
http://www.powerware.com/India/Service_Support/IN_Battery_Services.asp

You can email support at http://www.powerware.com/pp/Check.asp?key=code1
Good luck