automotive service

normal conditions in air conditioning readings

18-28 low, 213-250 high, 1 atmosphere, Room temperatures of 86-96 F (30-38C), Engine speed aproximately 1500 rpm, or 75% of engine rpm

air in cooling system(insufficient suction)

low side: 36 - 50 psi, high side: 284 - 356

indications: both pressures too high, low side piping is not cold

causes: air in the system

Defective expansion valve

pressure range: low side 30-36 psi, high side: 313 - 327 psi

indications: both pressures are too high

causes: improper refrigerant charge, defective expansion valve, or improper temperature sensor installation

Excessive refrigerant

Pressure range: low: 36-43, high: 327+

indications: Both pressures too high\

Causes: pressure increase due to excessive refrigerant, insufficient condenser cooling

Moisture intrusion

pressures: low: 18-21 psi, high:85-256 psi

indications : low pressure side alternates between a vacuum and normal pressure

causes: moisture has frozen in the air conditioner system, clogging the expansion valve

refrigerant does not circulate

Pressures: low: 0 - (-29.99) psi, high 71-85psi

indications low pressure side becomes vacuum, high pressure as listed above

causes: ac system is blocked by contamination or ice, AC system is shut off by defective expansion valve or temperature senor/ ac line from evaporator to compressor has kink in the line