My aircon system chills the air okay - no problem there. But when the temperature control knob is rotated to a warmer setting, with the aircon still switched on, there appears to be a sort of 'echoey-whirry' noise from behind the dash - possibly related to engine speed. Can't hear anything in the engine bay. Anyone experience the same?

Many thanks.

Mine's the same. I think the sound comes from actuator motors on the heater box. I get a similar sound when first putting the ignition key in (and when the AC was left ON and in AUTO mode). I am sure that similar sound is the recirculation flap opening/closing and is nothing to be concerned about. I haven't had my car long so still getting used to it....but vehicle AC is my business. I think the recirc.flap moves to the closed position when the ignition is off. That's quite a common feature with many AC systems. Try pressing the recirc.button on and off and see if you can replicate the sound. Does that help?

I'm not sure its actuator-related. The noise is continuous as long as the temperature is set to above chill. Pressing the recirc button makes no difference. Any ideas?

I'm not sure its actuator-related. The noise is continuous, as long as the temperature setting is above chill, and pressing the recirc button has no effect. Any ideas?

OK, understood. I listened carefully to the actuators moving on my car yesterday pm. I can definately hear the recirc flap actuator moving (more so into the open position) and also the individual distribution flap actuators (you'll hear those from the centre dash area). Those sounds are only momentary as the actuator/s operate.

But if you say the sound is continuous, I'd suggest/guess that your AC might be slightly low on refrigerant. Do you know when it was last recharged? It's quite common for noises as you describe to result from a reduced charge. Usually you'll hear a continuous noise from the expansion valve (regulator) and more hissing and gurgling than usual from inside the evaporator.

My car has a curious sound when the compressor engages. It's more audible from outside, and is a whistling sound. When the AC is activated and the compressor is running, the whistling is always there. The AC won't engage until the water temp rises slightly from cold (as per handbook) and as soon as the temp sensor allows the compressor to run, there's the whistling from the front of the engine bay! Tomorrow when there's a bit more time the car will be discharged and recharged with the correct R134a quantity (refer label on engine bay label) and I suspect the whistling may stop. My theory is that my system might be slightly down on refrigerant although like yours it cools the cabin superbly and the air is cold.

Other than those things I don't know what else to suggest.

Thanks - let me know how you get on with the re-charge/whistling sound......

Come to think of it, I remember a similar noise from the system in my old Golf GTi - whenever it needed re-charged.

A.

AC discharged, recovered, recharged yesterday. 490g refrigerant removed so 60g down from correct charge of 550g. No noticeable difference in cold air vent temperature. I don't expect the AC had been recharged since the car left the factory so 60g R134a loss over almost 3 years would be considered fairly normal. I should point out that in my professional experience ALL new or unregistered vehicles I have personally inspected in our workshops have left the factory with a low refrigerant charge - usually 5-10% less refrigerant than the manufacturer's spec. That covers vehicles from all European vehicle manufacturers. So perhaps my Roomster also left the factory with a low charge.

The whistling sound is still there and isn't affected by whether the AC is on or off (ECON). The whistling is still a mystery, but it isn't loud or annoying. I still suspect it might be associated with the AC compressor but I don't believe it's a fault. It may be an internal noise from the variable displacement compressor or possibly just drivebelt noise. I will do one more test on this, which is to check if the whistling sound changes when the AC is blowing flat out (speed 7) and on LO (in other words when the compressor is at maximum displacement/output). So really, nothing conclusive discovered so far.

CC

Edited 17 July, 200916 yr by schnauzerwagen
added detail

I'm wondering if your car has a broken actuator connection. When you select a temperature warmer than LO you hear the whirring noise, right? Could it be that the actuator motor for the temp control flap is working but doesn't stop?

I'm wondering if your car has a broken actuator connection. When you select a temperature warmer than LO you hear the whirring noise, right? Could it be that the actuator motor for the temp control flap is working but doesn't stop?

Thats what I think, when you select a higher temp the A/C will continue to function as before chilling the air. The only thing that happens is that a flap is positioned so that the chilled air is passed across the heater matrix. It sounds like the motor for this movement is playing up, its possible to have their positions recalibrated but it needs a dealer.

Manny - exactly! You described it better than I managed to. I don't get the "echoey" bit but the whirring - definately. Good luck FirstTimeSkoda. Lets us know your findings !