In a Texas Hill Country summer, an RV air conditioner that will not cool is not an inconvenience — it is an emergency. Before you assume the worst, here is what usually causes it, roughly in the order a tech will check.

Start with the easy stuff

Most “not cooling” calls are not a dead unit. Rule these out first:

  • Dirty filter or coils. A clogged filter or a coil packed with dust chokes airflow and kills cooling. This is the number-one cause, and it is cheap to fix.
  • Weak shore power. RV air conditioners are sensitive to low voltage. A long or thin extension cord, a weak campground pedestal, or a shared circuit can leave the compressor unable to start. If your A/C hums but will not kick on, suspect voltage.
  • Thermostat settings. It sounds obvious, but a thermostat in the wrong mode or a failing thermostat sensor fools plenty of owners.

The common real failures

If airflow and power are fine, it is usually one of these:

  • A failed start capacitor. This little part is the most common actual A/C repair. When it goes, the fan may spin but the compressor will not start — often with a click or a hum. It is an inexpensive, fast fix.
  • A bad fan motor. No air movement at all points here.
  • A tired compressor. Less common, and the expensive one. On a sealed rooftop unit, a dead compressor usually means replacing the whole A/C rather than opening the sealed system.

What a mobile tech checks

A pro will measure the voltage at the unit under load, inspect the filter and coils, test the capacitor, and check the temperature drop across the unit to see whether it is actually cooling to spec. That sequence separates a $150 fix from a full replacement — and you get the answer on-site instead of guessing.

What you can do right now

Turn the A/C off, clean or replace the filter, and make sure you are on a solid 30- or 50-amp hookup with a short, heavy cord. If it still will not cool, do not keep running it — a compressor straining on low voltage can turn a cheap repair into a costly one.

When the heat is on, get an on-site check fast. A local pro can usually have you cool again the same day, with the price in writing before any work starts.