Had to jump start now heater/ac wont work, no air blowing

SOURCE: After approx 40 min of highway driving the AC stops blowing cold

This is a problem solved by moderation. There are pressure switches in the system which cut off the compressor for too high a charge and too low a charge. The unit is suppose to cycle between a predetermined range, a moderation between high and low. If you were having problems before replacing the freon there is at least 1 pressure switch that could have been your problem in the beginning. If you have a manifold guage which shows high and low pressure you can tell when the pressure switch is open or closed. Some switches and for sure the autoparts store selling them can tell you the op[erating range of your switch. You can try just replacing the low pressure switch and fly blind without the manifold guages. Know how many ounces of Freon you put in? Compare to specs to see if you overcharged.

SOURCE: hyundai elantra air cond heater stuck on heat

sounds like the heat blend cable is either dislodged or frozen, the cable runs from the control head to the blend door located on the drivers side just above the gas pedal ,it is not an easy job to replace, i sugest to take it to your local dealer, its not that costly and they will know exactly what to fix.

Testimonial: "as my car is right hand drive i take it the position stated would be next to the centre console on side of heater air con box behind dash board. "

SOURCE: I have a 2005 Elentra

you are low on antifreeze. fill and check for leaks

SOURCE: AC will blow cold air for a few minutes then start

you have moisture in the system this causes your expancion valve to freeze up an stop working, thats why it works for sort time and when it de-freezes stars working again. you need to do a EVAC & RECHARGE with a good AC service equipment, specially attention to pull vacumm por at least 20minutes so you get all moisture out of the system.
Good luck

Testimonial: "Thank you Magoly, its working Thank you very much."

SOURCE: Hyundai accent 2001 will not start all lights work radio works heater fan works battery in 3 months old when I turn the key all i hear is a humming sound for about 1 min. than nothing. weather has be

The humming would be the fuel pump coming on. It should only hum for a few seconds, then shut off.
Your problem is with the start circuit from the battery to the starter, or from the ignition switch to the starter solenoid. Check the connections at the starter (the big cable) for tightness.
Is the battery charged up enough to turn the engine over? Check by turning headlights on and observe while someone turns key to crank. If they dim a LOT, then either battery is too low, or the starter is bad and needs removing for testing. If brightness doesn't change, then the circuit from ignition switch to starter solenoid is likely not working. Check for 12 volts at the small wire to starter solenoid with key in cranking position. If you have power there, the solenoid may be bad. Remove starter for testing. If no power at solenoid in starting position, then either the ignition switch is bad or the neutral safety switch might be the problem, or the wiring from the switch to the starter solenoid is not passing current.
Good luck.