1996, D2, 4.2Q ABZ .Automatic Climate Control.
 

Hi, Does anyone out there understand the link between the ECU and the Climate control head. I am convinced that the ECU is turning the aircon clutch off at light throttle. I have been told the the ECU can do this under lean mixture conditions.....no problem when using a bit of power and problem is not RPM related. This is driving me crazy. Main dealer has regassed and serviced etc, changed compressor speed sensor, fan stage resistor and relays and I have fitted an indicator to the compressor clutch feed to see what is going on! Any help most welcome. THANKS.

The compressor clutch is driven directly by the climate head unit, and there are a few reasons why it would turn off:

1) Full throttle
2) A/C turned off, or Econ selected
3) Evaporator freezing, thus more chill not required
4) Under pressure in refrigerant system
5) Over pressure in refrigerant system

This is assuming the A/C compressor is robust, and the wiring is fine, otherwise you could be looking at wiring / clutch faults.

Problems with the cooling fans, particularly the second electric fan could cause frequent over pressure problems leading to intermittent problems, especially when static running.