AC Charge Question
 

The AC system in my 94 E320 requires 2.2 pounds of R134. If system is evacuated and then 2.2 lbs is introduced, why are the high/low pressures checked?

They should be within spec.

Please comment.

Thanks

because there are a number of things that can affect performance. Compressor operation, evaporator valve operation, condensor blockage, etc. and other issues can be frequently pinpointed by comparing actual pressures with what is expected when system is operating properly. Plus, it's so easy to do. Think of your doctor listening to your heart with a stethescope...

One of the reasons caould be . . .
 

. . that the hoses being replaced; if so you won't end up getting 2.2 lbs b/c some residual is in the cables especially for a new set of cables or if they were 'discharged'. You would end up with less the 2lbs, so it's good to see what the gauges say. You can't go wrong and it's a good check.