Air Cond. Problems

I have a 94 Firebird 3.4 V6. The air cond. won`t cool good on a hot day. I put a new compressor and dryer on last summer and it worked fine for awhile. I tried to add some freon this year and at first the low side came up to around 30 to 40 lbs but then after a few minutes it dropped below 0. I ran it for a few days and rechecked the pressure, it was reading about 35lbs at first but after a few minutes it dropped again to 0. What is happening? It seems the system is still charged up, it just isn`t getting any circulation. Any ideas would be appreciated.

There may still not be enough freon in the system. The low side pressure will drop when the compressor clutch comes on. You could easily have enough in the system to get the system to come on, but not enough for it to do any good.

Sounds like a plugged TXV (thermal expansion valve)- on front of evaporator- easily accessed from underhood- probably has debris in it from previous compressor..........

Does sound like low system charge. Debris in the system could be the problem as well. A high side reading would be helpful too.

Sounds like a plugged TXV (thermal expansion valve)- on front of evaporator- easily accessed from underhood- probably has debris in it from previous compressor..........
I agree. Whenever you replace a pump you need to change the orafice valve. It is just a little plastic tube looking thing with a fine mesh "screen" in it and it sits in the evaporator at the main connection under the hood. They cost about $10 at the auto parts store. PAY ATTENTION to which way it sits in the pipe and put the new one in EXACTLY the same way. You'll need needlenose plyers to get the old one out (especially if it is crudded up.)

Don't forget that your '94 F-car uses a block style TXV- basically a variable orifice tube- that is mounted on front of evaporator- a little more costly than an orifice tube- but the same principle applies......

Thanks for the advice, I purchased a expansion valve yesterday and hope to install this evening. I will let you know if this solves my problem. Should I replace the drier again? I replaced it last year with the new compressor.

Thanks for the advice, I purchased a expansion valve yesterday and hope to install this evening. I will let you know if this solves my problem. Should I replace the drier again? I replaced it last year with the new compressor.
The drier should be ok still.

I put the new expansion valve and drier in yesterday. I pulled a vacuum and recharged and now everything is working great. Thanks for the expert advice.