A/C System Performance Check

A/C System Temperatures and Pressures, Checking

Observe the following:
- do not park car in sunlight
- condenser and radiator clean and free of obstructions
- compressor V-belt in good condition and properly tensioned
- air ducts for condenser and radiator properly installed
- air blend (temperature) flap cable is properly adjusted
- A/C compressor clutch engages when A/C is switched on


Test preparations:
- connect A/C pressure gauge set to low pressure and high pressure service valves
- open all air vents on instrument panel
- insert thermometer into left side air vent
- run engine until warm and set speed to 2000 RPM
- set fresh air blower speed to position 4 (high)
- evaporator water drain valve must operate properly and not allow air to be drawn in by fresh air blower

- set temperature control knob to FULL COLD
- push MAX A/C switch, E35 ON
- A/C compressor must run, fresh air/recirculation flap must close to outside air (recirculation mode)

- close windows and doors

- check A/C system performance according to the following charts





Outlet air temperature at left vent vs. ambient temperature

A - Outlet air temperature at left vent
B - Ambient temperature

- read temperature at vent after A/C compressor has cycled off for the first time
- compare temperature reading with chart

Example:
When outside temperature is 86°F, left vent outlet air temperature should be between 41°F-48°F.

If specified readings are not obtained,
- check A/C system pressures, following





A/C system high pressure vs. ambient temperature

A - Discharge pressure (high side)
B - Ambient (outside) temperature
C - Radiator cooling fan on low speed
D - Radiator cooling fan high speed switches OFF
E - Radiator cooling fan high speed switches ON

- compare actual A/C system readings with chart

Example:
When outside air temperature is 86°F, A/C system high side pressure should be approximately 247 psi. Radiator cooling fan on high speed.

If specified readings are not obtained,
- check A/C refrigerant charge





A/C system low pressure vs. ambient temperature

A - Suction pressure (low side)
B - Ambient (outside) temperature
C - A/C thermostat, E33
- switch closes at upper level arrow (A/C compressor ON)
- switch opens at lower level arrow (A/C compressor OFF)

- compare actual A/C system readings with chart

Example:
When outside temperature is 86°F, A/C system low side pressure should be between 29 psi-41 psi.

If specified readings are not obtained,
- check A/C refrigerant charge