Everything I have read anything over 275 head pressure is a problem. Is this true.
Depends on the system.... generally on the older systems, you were looking for a condensing temp about 30* higher than ambient... which at times will get you over 300. Newer high efficiency systems are different.
if a filter dryer is clogged would the line be hotter coming from the condenser and colder on the evap side and would it cause high head pressure? by the way, i changed my signature from tonydykes55 to apprentice because the more i read the less i realize i know