Question

1. a vehicles air conditioner blows cold air while driving at normal speeds, but warm while sitting at stop lights. the least likely cause of this condition is: an overheating engine. a weak electric fan motor. a frozen expansion valve. debris in the condenser fins.

Explanation:

Step1: Analyze overheating engine

An over - heating engine can cause the air - conditioning system to blow warm air when the vehicle is stationary as the engine heat affects the refrigerant's performance.

Step2: Analyze weak electric fan motor

A weak electric fan motor may not provide sufficient airflow across the condenser when the vehicle is stopped at stop - lights, leading to warm air from the AC.

Step3: Analyze frozen expansion valve

A frozen expansion valve would cause a lack of cold air both while driving and at stop - lights, not just at stop - lights. It restricts refrigerant flow constantly.

Step4: Analyze debris in condenser fins

Debris in the condenser fins reduces heat transfer efficiency. When the vehicle is stationary, the reduced airflow combined with the blocked fins can cause warm air from the AC.

Answer:

C. A frozen expansion valve.