A4 b6 air con woes
Discussion
I understand that the air con compressor is a known issue on these cars. The "prong" clutch fails over time and shears off.
I didn't want to be spending a fortune so I have been doing the labour part ( front of car off etc only to find that the compressor itself has seized.
I have had the compressor replaced with a pattern part, flushed, new dryer etc on re commissioning .
once hooked up the aircon guy advised that the system was working but was cutting out straight away.
a code check indicated flap motors, so I checked the fuses etc, and played with the controls, getting air out where I should be etc , just not cold.
When the aircon guy returned and plugged in still no cold air, he has powered the compressor directly and it works, so the next option is to get it round to the electrical engineers to see why the control unit is not activating the compressor.
Any advice / experience of the same issue previously / solutions would be gratefully received as what was hopefully to be £60 worth of clutch replacement has now turned into £350 of new compressor + labour fees!!
Thanks in advance, sorry for waffling!
I didn't want to be spending a fortune so I have been doing the labour part ( front of car off etc only to find that the compressor itself has seized.
I have had the compressor replaced with a pattern part, flushed, new dryer etc on re commissioning .
once hooked up the aircon guy advised that the system was working but was cutting out straight away.
a code check indicated flap motors, so I checked the fuses etc, and played with the controls, getting air out where I should be etc , just not cold.
When the aircon guy returned and plugged in still no cold air, he has powered the compressor directly and it works, so the next option is to get it round to the electrical engineers to see why the control unit is not activating the compressor.
Any advice / experience of the same issue previously / solutions would be gratefully received as what was hopefully to be £60 worth of clutch replacement has now turned into £350 of new compressor + labour fees!!
Thanks in advance, sorry for waffling!
You don't say if system was evacuated and recharged after fitting new compressor. This could only be done correctly if the compressor was running. If ...this was done and you are confidant the system has the correct gas charge/pressure the fault may ( one of potentially many causes) be the HP pressure switch . See my recent post re switch fix. Easy job if the system is correctly charged as the switch can be unscrewed and replacement fitted without gas loss. The switch mounting stub has a spring loaded seal that prevents gas leakage during replacement. Good luck
Hi, I have just been fault finding the AC on my A4 (all be it the 2.5TDI) so I am familiar with A/C systems.
Firstly, it might be worth pointing out that there are 3 core parts that make up any air con system, and you seem to have problems with all of them.
Mechanical system - A/C compressor, high and low piping, condenser, evaporator etc.
Electrical control of the compressor.
Electrical /mechanical control of the air flow.
Your first point ‘once hooked up the aircon guy advised that the system was working but was cutting out straight away’. It sounds like the A/C pressure is OK on initial start up (or the compressor would not initially run) and then some fault threshold is reached. Maybe Hi pressure in the A/C system, or electrical problem.
Your third point ‘get it round to the electrical engineers to see why the control unit is not activating the compressor’. The control module is activating the compressor (aircon guy advised that the system was working but was cutting out straight away) but the module appears to register a problem and then turns the compressor off.
Your second point ‘a code check indicated flap motors’ . It is unlikely that this is route cause, but it will not be helpful during the diagnostic process to have known faults on the system.
What diagnostic equipment do you have? For me I would want to see the A/C system pressure read either by A/C gauges or via the A/C pressure switch / transducer (diagnostic software such as VCDS-Lite).
Just thinking off the top of my head, I would start with why the original compressor seized. Did the pump fail internally and now there is debris in the system A/C mechanical system (not always cleared with a basic flush).
I would like to know if the A/C gas is circulating correctly (system not blocked or restricted) or whether the compressor runs initial but due to a restriction or blockage the A/C pressure rises to the point where the high pressure threshold is breeched.
If you need VCDS-Lite software here is a link: http://www.thinksystemsdiagnostics.co.uk/tools-tes...
Sorry if this sounds like a lecture
Firstly, it might be worth pointing out that there are 3 core parts that make up any air con system, and you seem to have problems with all of them.
Mechanical system - A/C compressor, high and low piping, condenser, evaporator etc.
Electrical control of the compressor.
Electrical /mechanical control of the air flow.
Your first point ‘once hooked up the aircon guy advised that the system was working but was cutting out straight away’. It sounds like the A/C pressure is OK on initial start up (or the compressor would not initially run) and then some fault threshold is reached. Maybe Hi pressure in the A/C system, or electrical problem.
Your third point ‘get it round to the electrical engineers to see why the control unit is not activating the compressor’. The control module is activating the compressor (aircon guy advised that the system was working but was cutting out straight away) but the module appears to register a problem and then turns the compressor off.
Your second point ‘a code check indicated flap motors’ . It is unlikely that this is route cause, but it will not be helpful during the diagnostic process to have known faults on the system.
What diagnostic equipment do you have? For me I would want to see the A/C system pressure read either by A/C gauges or via the A/C pressure switch / transducer (diagnostic software such as VCDS-Lite).
Just thinking off the top of my head, I would start with why the original compressor seized. Did the pump fail internally and now there is debris in the system A/C mechanical system (not always cleared with a basic flush).
I would like to know if the A/C gas is circulating correctly (system not blocked or restricted) or whether the compressor runs initial but due to a restriction or blockage the A/C pressure rises to the point where the high pressure threshold is breeched.
If you need VCDS-Lite software here is a link: http://www.thinksystemsdiagnostics.co.uk/tools-tes...
Sorry if this sounds like a lecture
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