the air conditioner in my car only works sporadically. on 2001 Nissan Altima

the air conditioner works fine occasionally, I never know when it will be working. The rest of the time it just blows out warm air. it had refrigerant added but that didn't seem to help. The mechanic said he would need to practically take the system out to find out what was wrong and it would be expensive so I just said no. Isn't there some way to find the problem without spending a lot of money?

Asked by for the 2001 Nissan Altima