A/C blowing hot air. Compressor activates and system has pressure.

Make sure the compressor is turning - check out the compressor clutch for operation. Also check the operation of the thermostat which turns on/off the clutch.

Sure the freon is in there? If you have a nasty leak it will come out as fast as you put it in. Also check the low pressure shut off valve. If stuck in the open position the clutch will not activate the compressor.

you will have to have the pressures checked, if the pressure is just high enough to operate the compressor it may not have enough Freon in the system to cool. also the rad cooling fan should be on when the a/c is activated, if its not it can cause a not cooling problem.

Most likely you have a leak in the system. The low pressure switch will not allow the compressor to run if the pressure in the system is too low. Could be a faulty switch or low pressure in the system. If the compressor is running, but you get no cooling, you have a leak.

A mechanic would check the system with a set of pressure gauges. If the compressor is running, the low side would read around 30psi and the high side would be around 250psi. That is how you know if the system is full of freon or not.
You may have to get a professional diagnosis to proceed. If you replace the compressor, the accumulator needs to be replaced and a vac pump is used to pull all of the air out before the freon is added.

see this causes and fix it. God bless you
Compressor Checks
Start with the compressor. Does it engage when you turn on the A/C?
If so, the compressor is working and the A/C system probably contains enough refrigerant to make cold air, so the problem is inside the HVAC unit. Replace the motor that controls the blend air door (this is a difficult job and best left to a professional since it involves tearing apart the HVAC unit -- about an 8 to 10 hour job!).
If the compressor does not engage when you turn on the A/C, see if it will run by jumping the compressor clutch wire directly to the battery (use a fused jumper wire). If the compressor works when you jump it, and the A/C blows cold air, the system contains refrigerant and the fault is likely a bad A/C compressor clutch relay or a bad clutch cycling switch or pressure switch.
If the compressor does not engage when you jump it, the problem is a bad compressor clutch.
If the clutch engages but the compressor does not turn (the belt will start to slip and squeal), the compressor is locked up and you need a new compressor.
If the compressor clutch engages and turns the compressor, but the A/C still does not blow cold air, the system is probably low on refrigerant and needs to be recharged.
Refrigerant Checks
Connect an A/C pressure gauge to the HIGH SIDE service port (located in the high pressure hose that runs between the compressor and the condenser in the front of the engine compartment). The gauge will tell you if there is any pressure in the system. Simply depressing the service fitting valve with a small screwdriver to see if any refrigerant squirts out is NOT an accurate check because it tell you how much pressure is in the system. It may still have some pressure but not enough to trip the low pressure safety switch so the compressor will engage.
If your A/C system is low or out of refrigerant, check for leaks, then have the A/C system vacuum purged to remove air. After the air is out, it can be recharged with the specified amount of refrigerant. It is important to get any air out as this will reduce cooling efficiency and may make the compressor noisy.
A/C System Functional Checks
If the refrigeration circuit seems to be working (refrigerant in the system, compressor running and building pressure), but there is still no cooling, the problem might be an obstruction in the orifice tube (located in the high pressure hose between the condenser in the front of the radiator, and the evaporator located in the passenger compartment). A blockage here will prevent the refrigerant from entering the evaporator or recirculating through the refrigeration circuit.
If the orifice tube is plugged, the high side pressure reading will be lower than normal, and the low side reading will also be lower than normal because no refrigerant is circulating through the system.
If the refrigeration circuit seems to be functioning normally (compressor running, frost or condensation on the high pressure line from the condenser to the evaporator), but no cool air is blowing out of the ducts inside the car (and the blower is working), the fault is likely a BLEND AIR door that is stuck in the HEAT position, or possibly a badly clogged cabin air filter that is restricting airflow. Another possibility would be a fault in the automatic climate control system such as a ad interior temperature sensor or control module.

several things can make the a/c blow hot air. if the a/c was working but barely blowing then you may want to check for a clogged cabin air filter(it is behind the glove box in the a/c box). since the a/c is blowing hot all the time now, try releasing the freon out of the system or have it recovered into a recovery machine. you may have OVERCHARGED the system and the high pressure switch is keeping the compressor from working.the best thing to do is have the system pressures checked to see if the low side is 35-45 psi and the high side is175-225 psi with the compressor working. if the pressures are not within these parameters then there is another problem.

Hi, there are several reasons your vehicle may be blowing hot air through the vents, such as a need to recharge refrigerant. There could also be a problem with the air conditioner's compressor. Vents will blow hot air if the compressor does not activate when the A/C is turned on. There may be an obstruction in the system, or the blend air door inside the HVAC unit may be stuck in the HEAT position so no air goes through the A/C evaporator.

Before you add freon to measure how much freon is clucht checks if the compressor is activated when you connect the air conditioner if the clucht not activated and have a good pressure in the system looks at low pressure switch that goes in the drier and that very often these are damaged, you also have to check the fuse and relay the compresor.Thanks

Make sure your system is fully charged with r134. The low pressure switch won't allow it to activate if there isn't enough in it.

Check the fuses/relay for the compressor. If good, bypass the pressure switch. If the compressor comes on, there is too little internal pressure. Have the system evacuated and recharged. If the compressor does not come on, it could be bad.