If your truck AC isn’t cooling, start by checking vent airflow versus air temperature. Strong airflow but warm air usually points to a cooling-system fault—often a dirty condenser, low refrigerant, or weak compressor output. If cooling drops at idle but works on the highway, suspect restricted condenser airflow or poor fan performance. Low refrigerant from slow leaks is also very common, while compressor failure is frequently misdiagnosed. Before replacing major parts, inspect the condenser face for debris, compare idle vs highway cooling, and check for oil residue at fittings. Matching the repair to the symptom pattern saves time and money.