View Full Version : a/c not cooling

27-08-2010, 11:26 AM
hi all,

i have 2008 Q7 3.0 TDI with BUG engine 27000 km on clock and 4-zone AC system.before two month car have cool air coming from front right side duct but very less or not cool air coming from left front duct so i check the system and found rear evaporator leak replaced it and fill gas the cooling is perfect for both side now after 2 months car came back with same problem no cooling from left front a/c duct.is there still a leak in system or something else.here is the measuring values from scaner when it cooling and when not cooling.

when cooling.
1-control current of AC compressor regulating valve N280 0.715 A
when not cooling.
1-control current of Ac compressor regulating valve N280 0.715 A
when cooling.
1-pressure in refrigerant circuit 15 BAR
when not cooling.
1-pressure in refregerant circuit 11 bar
sorry i donot have green liquid to cheak leaking but with making soap?

a8 tech
28-08-2010, 07:18 AM
the compressor is pulling amperage according to your readings so check the compressor clutch is engaging as you have sufficient pressure for the compressor to work.
check with the air con machine for high and low pressure readings when a/c turned on and see what the readings do.

30-08-2010, 08:19 AM
thanx alot john for your quick reply.as u know Q7 used PRESSURE REGULATING VALVE N280 type compressure instead of MEGNATIC CLUTCH N25 type so there is no clicking noice when compressore engage!
when connect to scaner no foult comes out.john i have SUN a/c machine does it will tell me the compressure pressure towards low and high side respectively?what is normal pressure in low and high side?compressore from DENSO.want to share some more values.

1-when cooling
a-control current of a/c compressore regulating valve N280 0.750 A
b-duty cycle of activation signal 87%
c-duty cycle of high pressure sender G65 43%
d-pressure in refrigerant circuit 15 BAR

2-when not cooling
a-same as above
b-same as above
c-same as above
d-pressure in refegerant circuit 11 BAR

once i recover gas,vacuum,recharge gas cooling is fine again during test drive after half an hour temperature at a/c duct start to rise from 45FH to 90 FH than totaly dead mean no more cooling.this is long story in short.waiting for your reply.

a8 tech
30-08-2010, 08:21 PM

interesting but need to see the high and low readings also feel the high and low pipes in the engine bay, are they both warm when the temperature increases?
Will dig the pressure readings out :beerchug:

24-09-2010, 12:17 PM
hi all,

m sorry for late reply about this issue actually i was waiting for the compressor so i replace my compressor with both expension valve and drier bottle and solve the problem.john pressure on low side is 2 bar and 12 bar on high side.i think something wrong with the PRESSURE REGULATING VALVE located in the compressor but this valve doesnot comes alone.