What does AC condenser do?
Since the condenser is a heat exchanger that causes the refrigerant to condense back to liquid, it will not be very effective when the fins get restricted with road debris. This causes system efficiency (cooling) to drop off.
What will a dirty condenser do?
Should the high-side pressure become high enough, a relief valve will vent refrigerant to control the pressure or a high-pressure cutout switch will cut power to the compressor preventing the high-side pressure from getting too high.