I want you to take the “air first” pledge. “I solemnly swear to check the system airflow before I connect my gauges.” If the system airflow is off, the pressures are going to be wrong, so there is no point in connecting your gauges until you know that both the evaporator and condenser are clean and the correct amount of air is moving through each of them. No amount of refrigerant can correct for a dirty air filter, you have to change the filter. I understand that not everyone in the air conditioning business has a tool for measuring airflow. But we are in the AIR conditioning business! Would you trust an electrician who worked without a volt meter? You don’t have to have a flow hood to measure airflow. There are several tools under $300 that do a good job. You can get a Fieldpiece hot wire anemometer, several companies make reasonably priced digital manometers, there are many inexpensive rotary vane anemometers, or you can get a Magnehelic gauge for less than $100. Dwyer sells an airflow meter for less than $50 that reads both velocity and inches of water column pressure. It is not in the same class as the other tools mentioned, but it is a whole lot better than nothing. Why should you invest in a tool that you have been doing without? For one, customers notice when you use instruments instead of guessing. But the best reason is because it makes your job easier. It is always easier to solve problems if you have good data, which you can’t get by holding your hand over the register. How many times have you added refrigerant to a system only to discover later that the coil was plugged up with cat hair? Wouldn’t it have been easier to check the airflow first and correct the real problem? Even if I can’t convince you to start measuring airflow, please at least check the air filter and check out the airflow with your handomometer before pumping refrigerant into a system that does not need it. Take the air first pledge!