A/c in jetta blows hot air, its been charged, compressor comes on.

low or no freon---- compression problem

Controller signals may not have to preach on hvac assembly, need to check the controller to the hvac line Motor Part Store Motor Parts Wholesale

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.

It may still be low on freon. It can hold several cans.
High side should be around 250psi and low around 35 or 45psi at idle if system is charged.
If you raise engine speed the low can drop below 20psi and switch off the compressor if the system is low on freon.
Could be a restriction in the system, bad relay, or bad a/c compressor-clutch.

You may have created an over charged condition and at this point the a/c compressor will cut off on high head pressures. This can be verified by installing gauges to the systems high and low side service taps and reading the pressures.An overcharged system will start the compressor briefly but soon cuts off once pressure goes to 350 - 400 lbs on the high side. Acceptable pressures for this system should be no greater than 250 high and low suction should drop to 40-50 psi.You might recover the charge and evacuate the system,then try bringing the charge back to proper level.A sight glass in the reciever drier really helps determining proper fill.Once all bubbles have dissipated from the sight glass during charging ,one should stop at that point to avoid overfilling.Too much freon is worse than a low charge especially in hot ambient conditions....

If it blew cold air after freon added and 5 days later blew warm, you may have a leak in the system. Also check and see if compressor comes on if not you may have an electrical issue, relay for compressor,coil on compressor, etc.......

The problem is the temperature blend door. Very costly to fix. I have a 2003 with the same problem. A diverter flap door that allows it to switch over from heat to air, is broken. The part is 400.00 and the labor itself is 800.00. The whole dash needs to come off. Everything is behind the dash. Sorry!

Look for leaks around the A/C hoses and compressor. You may just be low on Freon. When the pressure in your lines (amount of gas in your ac lines) is low, the ac will just cutout hence blowing hot air. try adding some freon.

Its a leak ...probably concealed like in an evap housing or rear air unit and lines (if it has that). Prob at this juncture I would remove all the freon and bring system into a vaccuum with a pump and see if it will hold vaccum for an extended period of time. A bad leak will not hold srong vacuum very long and much cheaper than wasting expensive and enviromental un0friendly refrigerants.

It is possible that the AC compressor clutch cycling is getting stuck in the off mode, this can be caused by a sticking expansion valve or a defective AC clutch control relay. One note u said u added more refrigerant to the system, if u over charged it you may cause damage to the compressor a $400 part and equal labor to replace, it might be a good idea to have the system charge checked by a shop that does AC work.