Air Conditioning Problem

The aircon is disabled in 4WD according to the circuit diagrams and the workshop manual. It appears to be in the same circuit as the aircon overpressure switch.

Martin

I had to compare an old manual car with an electronic one.

1. An old "manual" car only has a 4WD controller. The transfer box is put into 4WD using the lever, therefore the controller has to detect this and engage the vacuum, thats its only job apart from deciding that certain conditions are wrong and therefore it should refuse to engage the vacuum.

The old controller has 10 connections:

1: Vacuum control valve (output)
2: Vacuum control valve (output)
3. 4WD Light and ABS Controller (this must be an "output")
4. ECU (?)
5. Ground
6. Vacuum sensor switch (input)
7. 4WD Transfer box switch (input)
8. A/C Pressure switch (??)
9. Tacho
10. Power (input)

Therefore the only real inputs on the old controller are 6,7

2. A new electronic car has the 4WD controller and a transfer box controller. The transfer box controller looks at waht buttons you have pushed and controllers the electric motors that drive the transfer box. Using sensors and switches on the transfer box it then decides if you have been successful in your selection and then tells the 4WD controller to engage the vacuum. Therefore it then switches connection 7 on the 4WD controller to earth to signal it to switch the vaccum.

However there is the connection from the 4WD controller to the A/C, but its unclear wether the 4WD tells the A/C that 4WD is on or whether the A/C tells the 4WD that it is on? And both have connections to the ECU. The ECU seems to have master control of the A/C as it controls through relays the compressor and condensor. You should be able to force the the A/C by grounding these connections.