The Reatta's A/C control system will display warnings when a problem is detected. The following will help you understand what those warning mean.
The BCM tracks the pressure status of the AC system 3 ways. The first is via the low side temperature sensor. The second is via the low pressure switch . The last is via a high side temperature sensor.
The compressor is engaged by the ECM based on input it receives from the BCM. Be aware that the ECM will also disengage the compressor based on input received from other sensors including the throttle position sensor, coolant temperature sensor and the power steering pressure switch, even if the BCM is requesting that the ECM engage the compressor.The information from the Low Side Temperature Sensor will set codes B446 or code B447 when it detects that the low side of the AC systems gets too cold quicker than it should. A Low Freon warning will be displayed on the dash but the system will continue to function although it may not cool as well as it should.
When the Low Pressure Switch reports that the measured pressure on the low side drops below 10 psi for more than 3 minutes it will set code B448. A Very Low Freon warning will be displayed on the dash. The system will go into Economy mode and the compressor will be disengaged until the code is reset.
Sometimes this code will need to be reset by disconnecting the battery cable.If you are just getting code B448 without either B446 or B447, then you have a problem in the low side pressure switch. It will prevent the compressor from running even though there may not be anything wrong with the system other than the Low Pressure Switch.
Before replacing the switch you should check the following:
- Verify that the AC fuse #19 is good as this powers the circuit.
- Verify that the connector on the pressure switch is clean and properly connected.
- Verify that you have at least 12 psi or more in the system.
- Use a multimeter to verify that the switch is open with 12 psi or more in the system. (It should be normally closed under pressure.)
See photo for the location of the switch and sensors.
A new pressure switch should not be too hard to find at a local auto parts store. It can be changed without having to purge the system.