I've put freon in it using one of those el cheapo guage from walmart. After having a mechanic recover what little bit of freon was left, I hooked up to the low side port and immediately the guage went into the red indicating a "mechanical issue". So I put freon in it anyways. After a can and a half, the compressor would kick on and run but the lines never cooled and neither did the air. Is there something I'm missing? A buddy has a legit ac machine. He hooked it up and said something about no vacuum and that my compressor is bad. But the clutch kicks in like it should when it's turned on..any suggestions?
The AC system is separated into two halves, High side and Low side. When the engine is running and the AC compressor is engaged, the compressor pulls refrigerant (not Freon) from the low side and pushes it into the high side.
On the other side, the system is separated into high side and low side by either the orifice tube or thermal expansion valve (TXV) at the evaporator.
When everything is working well the low side should go to something around 30psi or less. The high side would then get up to 200psi or more.
If your seeing 100psi or more on the low side, two things could be wrong. Bad compressor, because it's not moving anything from low to high side. Bad TXV that is stuck open. Orifice tubes plug up but because they are just a hole they can't stick open.
The fact that the clutch engages as it should, does not mean your compressor is working properly. All the clutch does is apply torque from the belt to the shaft of the compressor. For the compressor to work the rest of it must be functioning and actually increasing the pressure of the refrigerant.
Speaking of which, Freon is R12, which has been illegal to make in the US since the 60's. Today's refrigerant is usually R134a (generally speaking, there are other types as well).