Sounds like he did it under a home warranty. If my experience is common, they did the minimum necessary to make it last through the warranty period. My Old Republic home warranty cost $900 and isn't worth the (scrap) paper it is printed on.

Had an old 64 Ford window fan. It had a swamp cooler mounted on the roof. Rigged it to circulate water through an ice chest using a windshield washer pump. It blowed ice cold real good.

$500 motor, two service calls. I paid $75 total. Yes they do the absolute minimum to keep it running. Nothing in terms of a tune up. I have one month left on the warranty that the realtor bought us a year ago.

This.

$500 and they didn't put gauges on the system?

Don't hose down the outside unit, putting chlorinated city water on aluminum fins will just speed up corrosion, scale, etc. The best you can do out there is build a shade structure that doesn't impede airflow at all.

Isn't there some kind of cleaner one can use that leaves a coating on the metal to defray corrosion?

When I cleaned mine, I didn't see any corrosion after three years post install. Fortunately, it's on the distal end of my casa from the coast plus under an overhang.

I have an inline filter that I sprayed with cold galv spray to protect it. Nothing else...

Bump....