Replaced a condensing unit for a friend. Did the startup and the suction pressure/temp crashes hard. Well, I tell the owner, looks like we're onto what killed your old compressor.
Head out to the garage where his furnace and coil are and open the furnace door. Wife comes running into the garage yelling - What did you do? There's dirt blowing out of all the vents for chrissakes!. Sure enough, the fan is return restricted and my opening the door dislodged thousands of dust bunnies.
Got to looking at the return - 2 12x16 floor level filter grilles in the hallway. Filters are clean, spotless really. Can't really feel any air moving at the grille faces. I'm thinking this is odd, so where is the restriction? Wen't back out to the garage and had the owner hold me by the back of my pants as I crawled under the furnace and looked up into the framing . . . Where the return air goes in the filter and up the wall, over the closet and down to the return box - was full of owens corning pink insulation!
I turned to the owner and pointed him at his drywall saw and told him - if any of your neighbors have problems with their a/c, have them call me.
That sound familar...
I had a similar experience last summer something like 108° days, homeowner complained system just could not keep up ran 24/7.
We had installed the system the summer before, Bryant 2 Speed really nice with a VS furnace.
FAU was in the garage just like yours, raise off the floor on a drywalled platform.
I noticed one of those large (really large) dog beds hanging thru a very large hole in the side of the platform. Old rover had chewed,dug his way thru the drywall. Homeowners thought this provided him some useful shelter and had his bedding in there for him.
Almost as bad as the famous answer " Filter, what filter honey"
Air Handler in attic
Round return run over to ceiling and has dovetails turned out at ceiling (not sealed)
Filter grille at floor level.
Open it up and look up into sheetrock chase where pipe should be connected to ceiling....
but NO HOLE. Just a solid peice of sheetrock.
No cooling, new house.
Original contractor left the country, took the money & ran.
Two units in crawl-out attic.
No filter in units.
No return air grills anywhere in the house.
All had been sheetrocked over, tectured & painted.
Homeowner came in carrying a couple of 20 x 20 return air grills.
Said contractor left them in the garage.
"Do you need these?"
The units were shoe-horned into a tight little attic.
I had to use a mirror to figure out where the return air duct was dovetailed into the sheetrock.
Took an educated guess, and got lucky on one of them.
The other was anybody's guess.
Homeowner had pictures of framing.
Made the 2nd one a little easier.