I drive a 200 Audi A4 (2.0). Recently, when Im driving fast (and outside temperature is high/hot), the AirCon automatically shitches to ECON and the car start emiting hot aid.

When I drive around town at low speed, the AirCOn works just fine

What might be the problem??

 

you might not have enough refrigerant or it might be a a/c compressor problem. best idea is to take it to a mechanic because it doesn't seem like an electrical problem.

 

on my 2002 3.0 tiptronic the a/c will turn off when you are at full power ie if you change down to pass then floor it the car will cut the compresser out till you slow down then it will reengage.

dont know if this is the same for manuals and autos.

 

I recently topped-up the refrigirant and I believe its just fine.

This weekend, I replaced the mass-air floor metre with the advice from a mechanic. I drove at around 140 KM/hour and it did not happen this time. Unfortunately, it was a cold day and i will have to observe it when its hot outside.

Some mechanic also suggested that maybe the fuel pump might need to be replaced. Can this be the some of the possible causes??

 

Fuel pump is unlikely. They last forever.
I would blame a dying relay for it, but I do not know which one.
They cost like $70 to $100 each.

Do you have moisture in the car. You should leave the car outside with opened windows and hood and let it dry.