ac did not work. so I opened up the system and found there was no orifice tube. I bought one, put it in and pulled a vacuum. added 134. it worked fine for a while. then it slowly quit. opened up again and found crud in the orifice tube. so I flushed the system put on a new pump, condenser, filter/accumulator and another orifice tube. pump will come on 1 second and the gauges both come up the same as if there is an obstruction. I was able to flush the evaporator out and I think it's flowing good but don't know. does the low pressure switch affect that? any help would be wonderful.