Compressor Control Logic

The A/C compressor will be controlled by PCM/ECM/BCM control logic under the following conditions:

Coolant Temperature
^ Disabled if engine coolant temperature exceeds 120°C (248°F).
^ Enabled when coolant temperature is 118°C (244°F).

A/C System Pressure
High
^ Disabled if A/C system pressure exceeds 2900 kPa (420 psi).
^ Enabled when A/C system pressure is 1998 kPa (290 psi).

Low
^ Disabled if A/C system pressure goes below 180 kPa (26 psi).
^ Enabled if pressure goes above 248 kPa (36 psi).

Evaporator Low Ambient Protection (ELAP)
ELAP is a BCM controlled cycling of the compressor clutch to prevent freezing of the evaporator core. FLAP is only enabled at ambient temperatures between 0°-20°C (32°-68°F).

Cooling Fan Logic
There are two cooling fans - a pusher and a puller. The fans run together at three different voltage levels to create three speeds or stages.
^ Low speed - both fans in series - 6 volts each.
^ Medium speed - both fans in parallel with resistor in series - 9 volts each.
^ High speed - both fans in parallel without resistor - 12 volts each.

The fan speed selected is based on coolant temperature or A/C system high side pressure.

Low speed
^ Enabled if coolant temperature exceeds 99°C (210°F) or A/C system pressure exceeds 1199 kPa (174 psi).
^ Disabled if coolant temperature goes below 95°C (203°F) and A/C system pressure goes below 799 kPa (116 psi).

Medium speed
^ Enabled if coolant temperature exceeds 102°C (215°F) or A/C system pressure exceeds 1695 kPa (246 psi).
^ Back to Low speed if coolant temperature goes below 100°C (212°F) and A/C system pressure goes below 1399 kPa (203 psi).

High speed
^ Enabled if coolant temperature exceeds 105°C (221°F) or A/C system pressure exceeds 2398 kPa (348 psi).
^ Back to Medium speed if coolant temperature goes below 103°C (217°F) and A/C system pressure goes below 2198 kPa (319 psi).