airconp pump

[ross]

having recently removed and rebuilt my 2.2 dci engine for the 2005 Espace, and now it is back in the car and running, I decided to have the aircon regassed to get it working.
when the aircon was turned on the pump did not work, the electromagnetic clutch did not pull in to drive the pump.
after removing the pump and checking the action of the electromagnetic clutch, on the bench, it worked.
unfortunately when reinstalled in the car it failed to work.
I have checked the fuse, and it was fine, so I am looking at other reasons for the electromagnetic clutch not to operate.
I am trying not to think that it could be the wiring, as this would be a nightmare of a job to trace, especially without a wiring diagram.
does anyone know if there are any other signals the pump needs to operate ?
I am puzzled by the function of the other electrical connector on the opposite end of the pump.
is this a pressure sensor, or a rotation sensor, or a temperature sensor, or what ?
any thoughts would be much appreciated.
Regards
Ross

[roy4matra]

having recently removed and rebuilt my 2.2 dci engine for the 2005 Espace, and now it is back in the car and running, I decided to have the aircon regassed to get it working.
when the aircon was turned on the pump did not work, the electromagnetic clutch did not pull in to drive the pump.
after removing the pump and checking the action of the electromagnetic clutch, on the bench, it worked.
unfortunately when reinstalled in the car it failed to work.
I have checked the fuse, and it was fine, so I am looking at other reasons for the electromagnetic clutch not to operate.
I am trying not to think that it could be the wiring, as this would be a nightmare of a job to trace, especially without a wiring diagram.
does anyone know if there are any other signals the pump needs to operate ?
I am puzzled by the function of the other electrical connector on the opposite end of the pump.
is this a pressure sensor, or a rotation sensor, or a temperature sensor, or what ?
any thoughts would be much appreciated.
Regards
Ross

This is more complex than you might first think Ross.  The electromagnetic clutch and air con. is controlled via the injection computer.  The computer switches the clutch via a relay as well as that fuse if I remember correctly.  The reason it is controlled by the computer is that when you demand full throttle, it cuts the air con. out so as to remove that load and give you all the engine power for the acceleration.

So you need to check the signal from the computer and relay as well as the fuse and wiring.  You really need the wiring diagram (as with any of these modern complex electronic cars) to be able find the components and to trace and check the wiring continuity end to end.

Roy