Why is my AC not cold in hot weather?

An AC system that's fine in spring and gives up at 95°F is usually marginal, not broken. Ambient heat raises head pressure, so any weakness shows up first on the hottest day: slightly low refrigerant, a condenser packed with bugs and cottonwood, a lazy condenser fan, or a cooling system already running hot. Practical checks: hose the condenser fins clean from the engine side out, confirm the fan spins whenever the AC is on, and have pressures read on a hot day rather than a cool morning — a cool-morning reading can look perfectly normal on a system that quits in traffic at noon.

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