[Jai]

Hey guys,


I think I need some advice...


About 1.5 year back when I got the car I started noticing that my fuel usage was very high, my power was a lot less and I heard whining (going up and down with RPM) when I had the AC on. I could especially hear it at a red light when standing still and then driving on.


Had it refilled at my friends dad who is a airco guy and he said that there was not enough gas inside the system. He was afraid that it had run too long without enough gas and that the gas was used as lubrication system.


So, I'm not sure if that is true or not but after the refill the system was ice cold and the sound was gone.



What is not gone is the high fuel usage and the fact that I have LOTS less power, it feels like 30% or so. I also have the feeling that if I drive let's say 50km/h and release the gas it will sort of start braking which it doesn't do as much with the AC turned off. Also, the car feels... tense... BUT it does blow cold and works :P At redlight it is more tense at idling, moving a little up and down, just slightly.



So, does anybody know if these are symptoms of a ac compressor that is starting to fail? If it fails am I likely to damage other components?



Would you just replace it?

[GreaseJunkie]

It's fairly normal to feel a slight loss of power with AC on. However what you're describing sounds like another issue entirely. On our cars, we have what is called a variable displacement compressor. It does not use a conventional magnetic clutch like other compressors. Typically if the compressor locks up, it breaks the sheer pins that hold the pulley so the pulley will just freewheel and it won't damage your belt. It's possible that there is excess drag from your compressor being run low on oil, but you would likely notice it all the time since there isn't a clutch.

How many miles are on your car?
Auto or manual?
Any check engine light on?

[Jai]

Originally Posted by GreaseJunkie

It's fairly normal to feel a slight loss of power with AC on. However what you're describing sounds like another issue entirely. On our cars, we have what is called a variable displacement compressor. It does not use a conventional magnetic clutch like other compressors. Typically if the compressor locks up, it breaks the sheer pins that hold the pulley so the pulley will just freewheel and it won't damage your belt. It's possible that there is excess drag from your compressor being run low on oil, but you would likely notice it all the time since there isn't a clutch.

How many miles are on your car?
Auto or manual?
Any check engine light on?

Thanks for the reply!


143.000 miles (230.000KM)
Auto 6-speed
No check engine light and no codes (will do another check tonight to be sure)


Looking at what you said I feel like maybe it's "normal" what I am feeling then. It's too bad I don't have any comparison. I think in 2 weeks when I will do my oil change my friend will bring his Z4 3.0i N52 and I'll see how that behaves compared to mine...

[GreaseJunkie]

Originally Posted by Jai

Thanks for the reply!


143.000 miles (230.000KM)
Auto 6-speed
No check engine light and no codes (will do another check tonight to be sure)


Looking at what you said I feel like maybe it's "normal" what I am feeling then. It's too bad I don't have any comparison. I think in 2 weeks when I will do my oil change my friend will bring his Z4 3.0i N52 and I'll see how that behaves compared to mine...

No problem man!

At that mileage, it could be that your cats may be starting to clog up. Time to order some catless headers, for testing purposes of course

Another thing to check, since you say it feel like it's braking off throttle: Drive for about 20-30 mins then go around to each wheel and feel how hot the wheels are. It helps if you can get a hold of an infared temp gun. Any excessive heat could be indicative of a brake caliper starting to stick or a collapsed brake hose.

[Jai]

Alright that sounds good! If I'll find something out I'll report back
Those catless headers are not allowed here in The Netherlands I'm afraid, will not get me through yearly inspection