today I was sent out on a problem child. A 5 year old builder grade 10 seer.
Evap coil with tev.
Good air flow, great sub cool and clean coil.
early spring coil froze up, tech out said bad leaky evep coil.
Installer replaced it.
Tech sent out again for no cooling and found lo back and high head (250 / 50)with partly froze coil. thought bad installer didn't pull vacume and over brazed.
New installer cam out and replaced coil with drier and new R.
yup
Tech out again same problem, system runs good for 20 mn or so and then head slowly goes up as back drops. Again this happens slowly.
Now it gets tossed into my lap.
Three , LOL , three coils with tev's and same problem.
now what i found was interesting.
When system would act up, Compressor amps dropped ( 3 ton - Bryant - 18 amps dropping to 12) Head would climb as back dropped and lost all hope of maintaining sub cool.
Shut down unit waited for about 15 mn and started a/c , Compressor won't start.
Added hard start and still nothing. So with good capacitor and hard start nothing. After waiting for about 30mn the unit started and all things good until - Well you know.
Long story short - Sold new system with new line set.

Any one come across this one before?