hi guys just put my air con on today for the first time and it hums when you change gear is this normal

aim asking my dealer when its goes for its first services to check it and see wot they say

If you mean that there is a slight humming sound when cabin fan is on 2-4bars setting, it's the cabin fan making this noise, I thought it was something on engine too but then checked that it was independent of engine rpm, did not change with speed and went away as soon as I turned cabin fan down/up. It is more heard during gear changes as the engine goes quiet for a moment after you press the clutch.

Unless you mean compressor making different noise when rpm changes during gear changes, then drivebelt tension could be a problem?

Hello guys, take a look here http://www.briskoda....__fromsearch__1 and then few months later http://www.briskoda...._fromsearch__1. I do also know from another forum, that this sound happens to many VW Polo 1.2Tsi.

Keep in mind that the compressor's part number is the same with some 1.9TDi engines used by VAG.

Also when ambient temperature was below -1 or -2 C and i was using the fan to heat the cabin (a/c button off) and when the engine was on temperature (blue light off) there was an awful whinning sound who was following engine's revs. As long as the ambient temp was over -1 C that sound dissapeared. Though the fan and the heater was working fine. No fault was able to be found at dealership. Weird.

The key point is whether the sound pitch follows engine rpm. If it does, then there is a problem with airco, if the pitch is constant, it's nothing on the engine.

Also, from the other threads, I noticed that in one case airco got replaced but the sound remained. this was likely due to airco clutch not being replaced together with airco, likely the clutch got worn out by the faulty compressor hence the noise. Both should be replaced unless the airco clutch can be demonstrated in pristine condition.

But key point is check if sound changes with engine rpm and follows the rpm (high rpm - high frequency)

Yes the sound changes and folllows the engine. The sound occurs only when the ambient temperature is above 27 C. No a/c liquid leak occured, no errors in VAS found, only the sound. The air comes out really cold and really fast. No hesitation for cooling.

Please let me think that not all of us can hear the sound(s). I drove a VW Polo 1.2Tsi that had the same a/c sound but the owner was unable to recognise the sound. He is also unable to recognise the sound that comes from his waste gate. Then I took him for a ride with my car, both as a passenger and as driver. He was unable to understand the sound of the a/c and the waste gate of my car.

I first time noticed that sound almost a year after I purchased the car which means that the a/c was working all 2010 summer period, then paused for winter season and was on again eight months later. Then I noticed the sound... After that I use to take a ride as a passenger or as a driver to any 1.2Tsi car I can find from friends and relatives. All makes the same sound(s). At least to my ears.

And the other thing is that the part No of the factory fitted a/c compressor was 5N0 820 803 and the new one is 5N0 820 803 C. Both can be fitted in a wide range of engines. Most of them big in size. Maybe the sound is due to our small engine size.

Here is a list of compatible cars http://www.teilehaber.de/kompressor.-klimaanlage-id17934810.html

Edited 25 May, 201214 yr by stratosg

I sometimes hear a slight wine that changes with the engine speed and only when the a/c is on. It was checked a couple of years ago and had a clean bill of health. It only seems to happen when very hot and humid so I assume it's just because it has to work harder.

ive been to my dealer and told them about the air con and they going to look at it they said they had no problems so far with the roomsters

but they had problems with the octavias air com the nut on the pully on the the air con does cume off so they will check it pete

Nut coming off is a known problem on Octy, I had it too on my Mk1 after just 6 months, best to tighten and glue it with superglue.

But I think on Roomster airco clutch is fixed with a bolt just like on the Mk1 Superb and it does not come off, in fact it gets tighter in use.

I must say that of the 3 cars, Mk1 Octavia, Mk1 Superb and Roomster 3, Roomie has by far the most efficient air conditioning, but also the noisiest. The noise I mean is cabin fan resonance noise and only on certain speeds (I think 3-4 bars setting), so nothing to do with compressor/clutch and not a fault, just cheap design. Still, given the volume of the aquarium , the airco works exceedingly well.

Edited 30 May, 201214 yr by dieselV6

+1 on the above

+2

It is a bit noisy, though, and it whines for a few seconds in some rare situations I do not understand...