Airconditioning Problems

97 Chezy Blazer 2wd. 98k miles, 4.3
I have been having some problem with my a/c. The dang thing work when it wants to. I have had a mechanic look at it but check the pressure and all that and put in freon(or what ever they are substituting for freon now) they thing will just work sometimes. no rhyme or reason i can see to it. Sometimes it works when driving down highway or in town, sometimes when stopped sometimes not. I replaced some sensor just aft of the coils on the line because someone said that might be it but nothing still. its really bafling to me
Any suggestions. Thanks

take it back to the machanic because he didn't fix anything, it could be the ecm, low pressure switch, or high pressure switch tellin the ecm to not enguage the ac pump, you chould have a freeze up condition with water in the line, lots of posibilitys with a/c

well the mech. didnt actually charge me anything. since it was a friend of a friend type situation. but he chacked a few things and said he didnt know because at the time i showed him, the dang thing decided to work again. JUst my Luck:banghead:

well the mech. didnt actually charge me anything. since it was a friend of a friend type situation. but he chacked a few things and said he didnt know because at the time i showed him, the dang thing decided to work again. JUst my Luck:banghead:

You first post says he put in unknown freon.
Your second post say he done nothing.
Now which is it or what all did he do or not do?
Now you may have a bomb ready to blow up or a air condition system full of stop leak and glue or what ever.
If he put in a butane mixer type freon better call 911 before you drive it again.
Or take it to a good air-condition shop and see if they can straighten up or fix the mess for you. But is is going to cost you double or more now.
Good Luck
MT

ok, then its in a control unit not a physical problem