First, you have to know what's wrong with it. AC repair really isn't a DIY thing.. you'll be much better off having a qualified tech do it.
You need gauges to repair AC.
why does my ford focus over heat when i turn the ac on
If the system is low or empty of refrigerant, you probably have a leak. Take the vehicle to the professionals for diagnoses and repair.
on the 2001 Focus we found the low pressure port in the passenger front wheel well, hopefully this is consistent with the 2002 model good luck
Take it to a repair facility. There are EPA laws on the process, which you cannot possibly adhere to, unless you're licensed and certified.
Take it to a mechanic.
What do you need? A diagnostic?, a repair? Do you know what problem is? What are symptoms?
Look in the FAQs.
its right in front of the passsenger side tire, you have to pull up the plastic part the covers the wheel
The AC recharge valve for a 2003 Ford Focus with a Zetec engine is near the firewall. It is the larger of the two lines going to the compressor.