Why did my AC cooling get worse after I rinsed the outdoor unit?

Rinsing the condenser coils with a garden hose on low pressure while the power is off is standard maintenace and won't damage the system. The fact that the air feels warmer now acutally points to a common diagnostic quirk: a dirty condenser can sometimes mask a **low refrigerant charge**. When the outdoor coils are caked in dirt, the head pressure in the system stays artificially high becasue the heat isn't being rejected efficiently. Once you cleaned that dirt off and the unit started breathing better, the head pressure dropped to where it shoud be, which then revealed that the system doesn't have enough gas to actually move the heat. Since you noticed the performance was already sliding after your professional service a month ago, it's highly likely you have a slow refrigerant leak or the technician undercharged it during the visit. A properly functioning system should be able to handle a clean coil and actually perform better, not worse. The water didn't break anything, it just stopped the dirt from acting as a 'crutch' for a failing charge. You should definitely call a tech back out and have them check the **superheat and subcooling** levels. Don't let them just add more refrigerant and leave; if it's lower now than it was a month ago, there is a leak somewhere in the lines or the coils that needs to be located and patched. Cleaning the indoor unit is always good practice for airflow, but it won't fix a temperature issue caused by the outdoor unit's cycle. If the air coming out of the vents is barely cool, you're looking at a mechanical or chemical issue rather than just a dusty filter. Get those pressures checked before the compressor starts taking on damage from running while undercharged.

Spot on. I’ve seen this a dozen times on older R-410A units. When you wash that gunk off, you're basially dropping the saturated condensing temperture. If your TXV is struggling or you've got a slow leak at the flare nuts, the evaporator pressure tanks. Did you happen to look at the liquid line? If it's frosting up or feelin' barely warm to the touch, you’re definately low on juice. I'd bet my Fluke 902FC you've got a leak at the service valves. Get a tech to do a nitrogen pressure test instead of just a 'top-off' or you'll be back in this same spot by July.

I had this exact thing happen last summer. I hosed mine down thinking I was being proactive, and it went from 'okay' to 'lukewarm' in ten minutes. Turned out I’d accidentally packed some of that wet muck deeper into the fins instead of washing it thru. I had to go back in with a proper foaming coil cleaner and a soft brush to realy get the grit out. Once I used the actual cleaner instead of just plain water, the temp at the vent dropped like 8 degrees. Might be worth checking if you just turned that dust into a thick mud layer blocking the airflow.