UK-POLOS.NET - THE VW Polo Forum

Hi,
I'm a newbie on this forum as I recently bought a second hand 2015 SE 1.0 Polo having owned a Nissan X-Trail for the last 16 years with no problems whatsoever!

As it's been very hot lately I noticed, coz it would be impossible to miss a loud growling noise and a vibration in the car when I put the AC on in traffic. Works fine when moving relatively fast. When I got home I popped the bonnet and the noise seemed to be coming from the radiator fan as it was running full speed and the plastic casing was shaking badly but when I turned the AC off it went slower and the vibration stopped.

So my question is, is this normal on these little cars and if not any suggestions how to fix it or maybe I need to get the garage that sold it to me to sort it. Polo has 29000 on the clock.

TIA
Olly

Sounds like the rotating part of the fan, is out of balance, either by virtue of its manufacture, or there is a chunk broken off a blade so that is creating a balance problem - or the plastic frame for that fan has been broken by rough handling or a front end collision.

Does the plastic frame that carries the fan assembly feel like it is free to move instead of being firmly mounted to the front of the car?

Wow you are right! Just above one of the blades as I feel around there is a piece missing, cracked off in the collision which I know this car was in prior to me buying it. Do you really think that missing piece could cause so much shaking and noise?

Oh yes, rotational balance is critical for it to run correctly!

Edit:- to sort that needs a new fan assembly, which is probably why it was not replaced when repaired!

Cheers mate, I'll notify the garage they need to fix it as I do have a 6 month warranty. thank you so much.

If that fan is left, it would start to break its mounting and that could send it towards the radiator and the repair costs would be even higher. So good plan to waste time trying to get it sorted out now while within warranty.

So the garage replaced the fan and all seemed fine until we hit the 30+ weather again....or should I say 38 degree weather last Thursday. Started the car and put the AC on....vibration and loud noise was back... Seemed the same as before. Texted the guy at the garage and he now says it must be the AC pump, I think he means compressor or belt as the vibration and noise only comes on when the AC is on and only when it's really really hot weather. He says coz it's so hot the pump has to work harder.

Thing is what would be wrong with the pump to cause it to send vibrations through the car? It sounds like a V6!

TIA
Olly

Before I forget, KwikFit recharged the AC sometime before all this happened but as I only just bought the car I don't know if this problem was already there or not. I'm reading that maybe an overcharged AC could cause this problem I'm having.
Olly

Overcharging the AC gas system would cause the running pressures to get too high and so the AC would protect itself and shut down.

One question, shortly after getting that fan replaced, did you try out the AC and so force that fan to run, and if so, did it run okay?

It could be that there is still something broken on where the fan is mounted and that has caused the second fan to lose a bit of a blade or two, so maybe check again for that damage as you did before.

I did and it seemed to be going fast but it wasn't a 30+ degree day. Problem is there aren't going to be anymore boiling days to test it. I'm wondering if there's a way to force the AC and fan to go full speed

I thought that AC only commanded the fast speed, engine cooling can command slow or fast speed depending on the cooling systems needs.

Oh okay so if the fan was spinning as fast as it does anyway that's why it seemed fine when I tested it at the garage but once the weather hit 30+ I'm guessing the AC compressor has to work harder??? So that's why the guy thinks it's something to do with the compressor or belt??

I'm perplexed but I'm no mechanic. One other thing to Chuck in is that there has also been a kind of knocking sound that seems to come from behind the glove box. It knocks a few times then stops......

Oh well I'll just have to wait and see what the garage comes up with.

Thanks again
Olly

I'd suspect if you are hearing knocking from behind the glovebox it will be a flap motor for the ventilation system playing up, it will have ended up with a dirty feedback track and it is now hunting as it can't get to the correct position the controller is commanding it to.

AC working harder when it is 30+C outside, it can only work as hard as its gas loading will let it, so I'd expect it to work okay, or be a bit low in gas charge and not quite keep the car cool, or if its been over charged it will simply shut down due to the running pressure at the high side getting too high - or something is wrong terminally wrong with the compressor and the cooling is not working at all, if that compressor suffers any internal destruction, there is a shear coupling which allows its pulley to break drive to it while still being able to turn as usual to allow the auxiliary belt to drive all other items like alternator and power steering pump.

I see.....I think. Thing is the ac seems cold enough no problems at all since the recharge, just this confounded noise and vibration.

Anyway, thanks again, I get the feeling this isn't going to be resolved this summer....
Olly

So just to clarify, are you saying, that you don't think a failing ac compressor or belt would cause the vibration?