Air conditioning only cools when idling

Welcome to 2CarPros.

The first thing that needs check is what the pressures are in the system. It could be too high or too low. Here is a link that explains how to evacuate and recharge a system. I am including the link because it shows the manifold gauges that are needed to check pressures. Often times, a parts store will lend or rent one to you.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

When checking the pressures, note the outside temperature and let me know both.

Here is a general link that you may find helpful too:

https://www.2carpros.com/articles/car-air-conditioner-not-working-or-is-weak

Let me know the results.

Take care,
Joe