Nissan Repair: 94 Sentra A/C, blower motor resistor, nissan sentra

Question
have a 94 Nissan Sentra, 1.6L for the last 3 yrs have been without a/c.
Took it too one mechanic, said I need a blower motor resistor, another one said an a/c compressor control switch. So, now I have changed them out. The a/c runs, but its not as cold as maybe it should be. Also, my son said that he heard a hissing noise. Thought maybe the compressor hadn't kicked all the way on.
I looked around and found a retrofit kit and 3 containers of freon w/cd, to increase the freon in the cars a/c.
Am I doing things right. Can you give me, your opinion on what else I need to do.
Thank you so very much

Answer
Hi Paula -

With A/C's believe it or not work more efficiently the more you use it. If it sits idle, especially for that amount of time, then it is not good for the system.

Can you tell me when they re-energized your A/C system, if the system was evacuated, in line filters replaced, flushed, vacuum applied to check for leaks before it was refilled? This would be the proper procedure for refilling.

If it is not getting as cold as it was, there is probably some blockage in the system from the long absence.

Hope this helps -
aloha
calvin