A/C compressor noise.

[Road2Ruin]

Just had a brand new ac compressor fitted. It is making a terrible noise when on, which dissappear when turned off! I am, of course going to be taking it back the garage, but any idea what it could be? Low refrigerant maybe? It's like a low grinding or whiring noise that gets worse the longer it is on.

TiA

[Lincsls1]

Multiple possibilities I'd say.

Firstly, is the 'new' compressor an actual brand new OEM part or a refurbished part from a local motor factor.
It could a faulty 'new' compressor, maybe the bearings, more likely if a refurbished part not done right. The noise going away when turned off because the 'load' is removed from it even though the pulley will still spin.
Otherwise it could be the belt is on to tight, or one of the tensioner/idle pulley bearings has now failed since the new compressor has been fitted.
In terms of low gas, doubt it because the system wouldn't work as the low pressure cut off would kick in. Possible I suppose though.
But, all this is guess work, just take it back and think no more off it.

[Road2Ruin]

Pulley bearing sounds a distinct possibility and makes sense. It is a new, but not oem part...they were too expensive.

Thanks

[JakeT]

When components of a system are replaced, a certain amount of oil is needed in the system to replenish it. May be that.

[TonyRPH]

I had my aircon regassed a while back, but it must have a leak - and as the gas ran out, the compressor became increasingly noisy.

Maybe yours has a leak?

[Road2Ruin]

Sounds like too many possibilities to say for sure. Just wanted to have an idea before I call them.

Thanks

[clowesy]

Bearings could be the culprit. Possibly knackered, or could be an incorrectly tensioned belt. As already mentioned, best taking it back as there are many possibilities.

When the old compressor was removed, how much oil was in it? Was the system oil topped back up with the amount lost?

Low refrigerant will lead to poor oil recirculation, but as mentioned previously, there will be a low pressure cut off so once the system has lost any significant quantity, it just won't run. An overcharged system with too much refrigerant can cause some excess compressor noise due to high system pressures, but that's unlikely to be noticeable unless the system is under high load.

[Road2Ruin]

No idea on the levels of the old system. I just assumed it would be topped up if needed. Sounds like a metal on metal whiring noise that gets worse when hot. Could be oil, could be gas, could be bearings...we will see.

[E-bmw]

Definitely sounds like bearings on something from what you describe.

It is my understanding that the lubricant in A/C is actually entrained in the gas, so oil will be there naturally unless you have a leak.

[tim0409]

Thread resurrection….did you ever find out what was causing the noise as I have a similar issue after a replacement compressor was fitted?

[Road2Ruin]

tim0409 said:

Thread resurrection .did you ever find out what was causing the noise as I have a similar issue after a replacement compressor was fitted?

Yes I did. It was too little oil put in the new compressor. The garage that fitted it didn't follow the manufacturers guide and guessed. Good luck.

[21TonyK]

I’m having exactly the same with a new compressor and even swapped the old one back in with same issue. Calculating the oil level seems tricky as you may have residual oil in the system.

I have one mini which is silent and another whirring and grinding.

[stevemcs]

21TonyK said:

I m having exactly the same with a new compressor and even swapped the old one back in with same issue. Calculating the oil level seems tricky as you may have residual oil in the system.

I have one mini which is silent and another whirring and grinding.

Yours may very well be the crank pulley

[21TonyK]

stevemcs said:

21TonyK said:

I m having exactly the same with a new compressor and even swapped the old one back in with same issue. Calculating the oil level seems tricky as you may have residual oil in the system.

I have one mini which is silent and another whirring and grinding.

Yours may very well be the crank pulley

Unfortunately/fortunately the one with the knackered crank pulley is not the one whirring. But it s something that it being done on the one that is anyway as the crank seal is weeping so new seal, pulley and belt. While it s being done I ll put more PAG in the compressor. How much I m yet to work out!

Edited by 21TonyK on Monday 31st August 19:44

[stevemcs]

21TonyK said:

Unfortunately/fortunately the one with the knackered crank pulley is not the one whirring. But it s something that it being done on the one that is anyway as the crank seal is weeping so new seal, pulley and belt. While it s being done I ll put more PAG in the compressor. How much I m yet to work out!

Edited by 21TonyK on Monday 31st August 19:44

If you look on NRF’s website it states how much

[21TonyK]

stevemcs said:

If you look on NRF s website it states how much

I used that for reference originally as the new compressor is NRF and that had some install instructions. But…. It gets a bit unclear. The NRF compressor comes with 60ml of PAG in it. Then specifies the amount at install 135 so drain that and top it up. Then for a new condenser various sources say add 30-60 ml depending what you read. Then there’s an amount for the pipe work and evaporator if you completely clean the system. I’ve replaced the compressor and condenser with a total of 125 in the compressor but nothing in the condenser. I can only really experiment now so I am planning to add another 30 to the condenser and 30 to the condenser then regards with a gas that contains oil as well.

Can only hope at this stage!! If that fails then it will be case of handing it over to an aircon specialist.

[alabbasi]

AC compressors usually come pre filled with a little bit of oil. This needs fo be drained and the correct amount of oil needs to be added, otherwise it will grenade..

Also check the clutch by removing the belt and see if it's grinding when you turn it by hand.

[tim0409]

Road2Ruin said:

tim0409 said:

Thread resurrection .did you ever find out what was causing the noise as I have a similar issue after a replacement compressor was fitted?

Yes I did. It was too little oil put in the new compressor. The garage that fitted it didn't follow the manufacturers guide and guessed. Good luck.

Thanks! I had disconnected the electrical connector to the compressor until I had time to investigate. I wanted to replace the condenser (it was cheap) so I removed the bumper yesterday and couldn't believe the amount of detritus I found embedded on the radiator.

I've replaced the condenser and removed the new compressor to check the oil level now I have information from the Skoda workshop manual. The total oil fill for the system is 75ml, and it gives you a percentage breakdown for each component, and 70% of the oil would represent the amount in the compressor, condenser and drier so I reinstalled 52ml.

I still need to connected the compressor back up and re-gas, and if it still making the noise I've either probably damaged the compressor previously or the pulley bearing is gone. I still think I maybe had too much gas in it previously. Will report back!

[21TonyK]

Watching this as I still have a mini with a less than silent compressor.

[Hassan88]

The quickest way to separate a compressor problem from a belt or pulley problem is the A/C on/off test — if the noise changes or disappears when you toggle the A/C, it's clutch/compressor; if it's constant, look at the belt, tensioner and idler pulleys first. A compressor that is getting louder over months usually points to internal wear or low oil rather than a bad clutch, so it's worth checking the manifold gauge readings (a low-side reading that keeps climbing with a high head pressure is a red flag). If it is the compressor, make sure the new one is primed with the correct PAG oil amount before fitting, as running one dry is what causes that whirring/grinding failure. No point condemning the compressor until you've checked the belt and pulleys, though.