A.c. blows cool air than blows regular air, when driving.

I would suggest an AC service (evacuate & recharge)

You would need to know what the system high & low side pressures are reading when this happens. It could simply be low on refrigerant, or it could have component failure - the pressure readings should lead the way to the problem. If the pressure readings are ok while the problem is occurring, the car would need a scan for HVAC trouble codes. If pressures are ok, & no trouble codes, check into the temperature door operation in the dash