when you say that i figured it was low on freon - i am also figuring that same thing.
And that is because there is a freon leak.
if that was the case, then that situation still exists (well, maybe not since it could have been an o-ring that you replaced).
But there is a "snake in the grass" here, since the mechanic said that he did not fill it all the way but only so that the problem described does not happen.
So, are you low on 134a because of a leak - or is there no leak and it is not all the way filled ??

 

The place I took it to found that the low side service port had a leak....the valve itself where yoy attatch the thing to add freon to the system. He replaced that for free for me. I am not sure whether or not to add freon myself. Last night I figured I would run the A/C on the way to work and it got cold. Ran fine...now if this was during the day and it was hot, it wouldnt have been very cold at all...what would cause this? Should I add a little more freon and see what happens? I saw the arctic chill brand of freon over at Wal-Mart the other day and it said that it got colder than standard 134-A and that it was compatible with retrofitted systems and residue of R-12...and said something else about its ability to save gas. What are your opinions on that stuff???

 

Oh...I forgot to mention in response to Jake's last response about the expansion valve. I did purchase one from Advance Auto Parts and my father put it in before I took the car to that A/C place. The guy there told me that I should have gotten what is called the R-134a version of that valve. I thought he was full of s*** on that because I would think there wouldnt be that much difference. As to the evap core...the thing where the expansion valve is installed to...under the pass. dash next to the blower motor...noticed there was some dirt inside. Cleaned it out and noticed dirt and debris inside of the blower motor and cleaned that out too.

 

cant see how you say "dont know" - the guages tell you if you add or not.
should have a guage- years ago they would be packaged with a can of freon - were not pro guages but served the purpose - have not looked at them for a long time.
get a guage - if it shows low then add freon

 

What I meant about dont know is that i didnt know whether i should add freon or not because of locking the compressor up. I have 2 a/c guages and I didnt know whether or not these guages would be accurate cause they look cheap.

 

well, what do the guages read ??

 

I converted an 82 Celica I used to have. I changed the compressor, reciever dryer and every O ring I could get to.
I did not get as cold with the R134 and it need to be recharged after two years.

I've heard that the molecules in R134 are a lot smaller and will find ways to leak where the R12 wouldn't.