Hey there,
My Fiat 500 TA has a high frequency noise when: 1) the AC is turned on AND 2) the engine rev is about 3000rpm, on the way Down from for instance 4000rpm.
I've never noticed the Sound when the AC / compressor is turned off. It's a quite high tone "screamy" Sound, it only lasts for some Seconds, then it disappears again. And, the Sound doesn't appear every Time the engine revs are at 3000rpm, only now and then. That makes it so difficult to detect.


I had the Car to my local Garage, but then the Noise didn't appear.


What is this? Please, help me if you have experienced something like this With Your TwinAir Engine - I have to take it to my Garage again before my Guarantee expires in one Month...



HELP!!

Drive belt to the compressor slipping perhaps?

There are 2 threads with same problem
other one here https://www.fiatforum.com/500/273939-twinair-high-pitch-engine-noise.html
I just posted this on other thread

Aussie500nut said:

When we got our TA new there was a turbo noise
We were used to turbos as the "other" car was a Landcruiser TD, albeit a big diesel compared to a tiny petrol engine

But the noise wasn't consistent and that didn't seem right so I took it back to the dealer.
By consistent I mean sometimes it was a bit louder and at other times it had awhistle - it should be the same under the same operating condition all the time, power on, power off etc

Turned out an "O" ring on the turbo hadn't been fitted correctly
Now noise is consistent - always the same under boost or at cruise

Hope this helps
Cheers

Click to expand...

Hi

When reading your question the symptoms you describe i.e.: it only happens when the air conditioning is switched on make me think its the belt slipping on the compressor pulley.
The compressor pulley spins all the time the engine runs, its connected to the shaft that drives the compressor buy a magnetic clutch arrangement.
Once the air con calls for the compressor to 'kick in' the electro magnetic clutch places a a bit more tension on that pulley which might be causing the drive belt to slip across that pulley a little as it starts. Check the drive belt tensioner.

When you start the TA from cold at idle (with the radio turned off) and the aircon on you can hear a click and the engine revs slow as the compressor drive clutch engages and then another click and the engine revs go a little faster as the compressor clutch disengages. during low idle this happens about every 30 seconds.
if you open the bonnet and look to the left where the aircon compressor is you can see it all happen.

hope this helps

mg