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C5 X7 A/c Cuts Out After 30 Secs


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#1 nemdis

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Posted 09 June 2019 - 10:13 PM

New to me 2008 C5 X7 2.0 HDI VTR+

Symptoms
Start engine (on tickover) with A/C on temps set to LO
After a few seconds A/C clutch cuts in 
After 30 secs A/C clutch drops out

Checks/Work done so far
Clutch operation normal i.e. 12V > on, 0v > off
Regassed with 625gm R134a
No leaks
Manifold gauges show 55psi with engine off and cold. (Ambient temp around 13 degrees C)
During 30 secs run time LP drops to 25psi, HP rises to 120psi
Rad/Condenser fan runs continuously from engine start but stops soon after the clutch drops out
Climate control fan speed inconsistent with panel readings i.e. pressing speed increase/decrease buttons have no effect
Heater fan control module has been replaced but symptoms unchanged

Any advice would be appreciated.
Many thanks,
Mike


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#2 paul.h

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Posted 10 June 2019 - 10:09 AM

Looking at the Citroen service box procedures, I am not 100% certain but the high pressure seems about right (9-10 bar = 130 - 145 psi) but the low pressure is low, should be about 3 bar (=44 psi). Possible causes include the filter/dryer being blocked/saturated or the pressure relief valve iced up.

 

If it is the dryer it seems to come as part of the condenser so would be expensive.



#3 nemdis

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Posted 11 June 2019 - 10:26 AM

Thanks for this.  Your comments are really helpful in working out what might be going on. 

 

Having checked the refrigerant piping it seems the drier is on the HP side of the compressor but upstream from the HP manifold connection point. So, if the drier is constricting the flow it might be enough to drop the pressure from say 140 to 120?

 

According to what I've picked up from the Internet, low LP is normally attributed to lack of refrigerant, but clearly not in my case. This seems to leave a blocked evaporator or faulty LP switch as leading possibilities? (Not sure where the LP switch is?).

 

I gather Lexia can me used to monitor goings on in real time. Mine's broken. Guess it's time to fix it!

 

Thanks again,

Mike


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#4 paul.h

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Posted 11 June 2019 - 01:15 PM

I am not sure but the low pressure switch might be on the compressor and the high pressure switch on the condenser on one end. A diagnostic with the Lexia is the best way to help decide what is wrong. In the parts diagrams the switch on the condenser is shown but not one on the compressor, apart from an electrical connection.



#5 paul.h

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Posted 11 June 2019 - 01:25 PM

A couple of topics to read for info, in this case the engine cooling fan was faulty

http://www.citroen-o...-manual-aircon/

http://www.citroen-o...on-wont-engage/



#6 nemdis

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Posted 11 June 2019 - 09:07 PM

Thanks. 

Seems you put some time in there too!

Mike


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#7 nemdis

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Posted 14 June 2019 - 09:54 AM

Problem fixed. I picked up from another post that Chinese versions of the heater fan control module are often not up to the job. I managed to get my Lexia going (on my Macbook Air) and this confirmed: Permanent fault air blower supply. I did wonder if this meant the rad/condenser fan but all the same I ordered a Hella brand heater fan control module. Now all is good. Hope it lasts!

 

So, thanks to forum posters, particularly paul. h


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#8 paul.h

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Posted 14 June 2019 - 10:07 AM

Good to see you have fixed it and it was probably the lowest cost item to replace. I have read before that cheap copy parts are not always good enough so prefer to buy them from a dealer. Copy parts are not always that much cheaper though, I once bought rear lights from eurocarparts for a C3 and they did not fit. I returned them and got them from a dealer and they cost the same but also included the bulb holders.