Grayedout said:
So had a look on the half hour journey home and the Evaporator out temp (5) ranged from 31 - 33 and the pressure sensor (10) only moved between 06 & 07. What's the units for the pressure and what's a typical value?
Also noticed pressure did not change when I manually turned the air con on and off.
The pressure is supposed to be in MPa (Mega Pascals) where 1 MPa = 1 Bar
Normal operating range is 10 to 15 Bar
Those pressure values indicate either - not enough gas in the system, or, the pressure sensor is faulty, or, the compressor is not working internally.
It comes down to the statement in #1 made by the people who re-filled the system "they can see the clutch kicking in but still not working".
"they can see the clutch kicking in but still not working" is Valid
The engine ECU triggers the compressor clutch relay (the relay energises the compressor clutch). The engine ECU only does this when the aircon control unit gets correct signals from all the sensors in the aircon system, and then communicates (via the gauge control module) that the engine ECU can trigger the compressor when the engine ECU is ready to do so.
Thus, if the inner part of the compressor
is rotating (i.e. they did "see" this), then all sensors and relays in the aircon system must be working, and the compressor is simply not compressing. This would show up as low pressure in the system, which the inbuilt diagnostic shows.
"they can see the clutch kicking in but still not working" is not Valid
This indicates one of two possibilities
1. as well as being incorrect about the compressor clutch, they were also incorrect about the gas refill i.e. still not enough gas in the system - maybe there is a leak at a joint where the gas is lost under pressure (when compressed)
2. although incorrect about the compressor clutch, they did refill the system properly, and there is no leak. In this case, since the inbuilt diagnostic shows low pressure, then the pressure sensor is faulty i.e. the controller tells the engine ECU to trigger the compressor, which it does, the compressor compresses the gas, but the faulty sensor shows no rise in pressure, so the controller tells the engine ECU to stop. The aircon controller then times out and tries again.
checking whether "they can see the clutch kicking in but still not working" is Valid or not
can you hear the compressor at all ?? If you cannot hear it at all, then the compressor is possibly faulty.
As a final check, go to my "diagnosing aircon problems" thread
http://typeaccord.co.uk/forum/topic/10382-diagnosing-aircon-problems/ and do the first check. You do not need the key in the ignition. Just remove the compressor clutch relay (as shown in the pictures in #1 of that thread) and connect a wire from pin 2 of the empty relay socket to the battery positive, and you should hear a "clunk" from the compressor clutch. If you do hear a "clunk", remove the wire, leave the relay out, and start the engine. Set the target temperatures to LO, go to manual control of the A/C, set A/C ON, blowers to max, then connect pin 2 in the relay socket to battery positive,and feel if cold air is blowing. DO NOT LEAVE IT LIKE THIS FOR MORE THAN A MINUTE. If you can feel cold air blowing, hen the pressure sensor is faulty, otherwise, the compressor is not compressing (or no gas in the system). Note that doing this check with the engine running on the system in the diesel may bring on the "coil" light on the dash. This should eventually clear itself.