[vega43]

2005......what should the low side pressure be. right now it reads 50....and when the fan comes on it drops to 40.....fan off, back up to 50. outide temp 85-90.

 

[alexklm]

Some numbers

With such ambient temperature, static pressure (with engine not running) should be much higher (around 90-100 psi, in accordance with pressure chart). If gauge shows static pressure 50 psi with ambient temp 90, it means that amount of refrigerant is low (or gauge is broken).

When cycling, pressure range changes between 21 and 45 psi.