I have a/c which worked... For about a week after I put some 134 in. Now I'm wondering why it's broken. I have suspicions based on previous posts here, and that I hear a hissing in about the glovebox area, that it might be the evap valve. Is there any way to positively or negatively diagnose this problem without the gauges? It'll be a while before I have access to gauges, and I'd like to figure out what the problem is now. Any other ideas about what problems it could be?
Also, am I safe to throw at least part of a can in so that at least prom is comfortable? I'd hate to overcharge and ruin smth, but not sure how easily that happens.