The recommended pressure for a home refrigerator using R134A refrigerant is between 2 psig and 150 psig. Readings that are higher or lower indicate an overcharged system.
Although the low side pressure should be around 2 psig, at times it can fluctuate from 0 to -3 psig. If the low side pressure rises to over 10 psig, the system has too much refrigerant.
When the refrigerator's compressor first begins running, the pressure will appear higher than normal. After the compressor runs for a short time, measure the pressure to get an accurate reading. If the pressure remains high, the system is probably overcharged.