My 2010 Scout has just started making a hissing noise when the AC is turned on. Once turned off the noise stops. It appears to be coming from behind the dash, primarily through the air vents above the stereo. I've had the car from new and not had any problems up to now. Anyone have any ideas before I take it in please?

That is the refrigerant boiling off through the evaporator. Some noise is normal if the car still and the fan turned down. Excessive noise can be a sign of refrigerant shortage but this would be accompanied by poor cooling performance.

The normal noise is like the one your fridge freezer makes at home, that hissing/whooshing noise you can sometimes hear.

Also, the compressor can vary its output which could lead to slightly different noise at partial load. Max out the system and see how the cooling performs.

Thanks for that dstev. I thought it may be low refridgerant but I'm surprised it's happened so soon. I've only had the car 18 months ish and I'm just coming up to 15000 miles. Unless there is a ruptured joint/pipe of course.

Thanks for that dstev. I thought it may be low refridgerant but I'm surprised it's happened so soon. I've only had the car 18 months ish and I'm just coming up to 15000 miles. Unless there is a ruptured joint/pipe of course.

Have a look at the condenser on the front of the car to see if it has taken any big hits from stones etc.

The condenser is right at the front then it's the I/C and then the radiator behind that. Unfortunately it is quite vulnerable where it is.

If it has lost gas it'll be a damaged component. The compressor drive seals rarely leak these days as they are constantly lubricated as the a/c compressor runs all of the time.

My previous Octavia still has a full gas charge and it's done over 150,000 miles so I think you may have been unlucky if it has leaked.

Cheers for that. I'm popping into the garage on Saturday for them to have a quick look. I hope it's not condenser damage as this won't be covered by the warranty. I had no end of trouble with my old Octavia's Climatronic so luck doesn't seem to be with me on this. I'll let you know if they find anything.

Ok. Good luck with it

Well there is an error code on VAGcom, I didn't get the number but the error message was "System low pressure". So as you alluded to, there is a leak on the system somewhere. The cooling performance was rubbish as well. I had a good look, with the mechanic, over the bits that are easy to inspect and we couldn't see any obvious damage. It needs to go through the routine of dye filled recharge to find the leak. Hopefully a failed part rather than a damaged one and covered by the warranty.

Hopefully it will be that warranty related failure rather than a whack to the condenser or something like that. Could be a loose mechanical fitting in the engine bay.

Well it took a week but I have it back now. It turned out to be the compressor so fortunately covered by the warranty. There is some sort of Skoda bulletin relating to this problem, although not that common I think. I don't know the details of this but essentially it's advised that when the compressor is replaced the condenser is also replaced, so that was done too. Hopefully sorted for good.