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Discussion Starter · #1 ·
When the air con is on there is a squealing noise from the engine bay as in the video.
video

Is this only the electro- magnetic coupling / clutch or do I need to replace the entire air con compressor?
 

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Likely that your electromagnet has weakened, clutch has burnt up, or that the electromagnet is not being supplied enough voltage by the fan control module. For me it was all 3, with the root cause being the fan control module.

I made the mistake of only replacing the electromagnet/clutch assembly and not the FCM too, which meant I burnt up another clutch assembly due to the low voltage going to the electromagnet.

You ideally want to check voltage to the compressor while under load. I did this by piercing the wires to the electromagnet with drawing pins and probing those. 12v with AC on but the magnet disconnected, does not mean 12v with AC on and the magnet connected.

Could also be fan noise? Unless you've narrowed it down to being from the compressor.
 

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Discussion Starter · #3 ·
Thanks, I'll research the fan control module.
If the noise is intermittent, eg tonight there was no noise, does that suggest the clutch / electromagnet at fault rather than FCM?
 

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Not sure, potentially clutch/electromagnet slipping depending on how high the pressure is in the AC system. Warmer weather = higher pressure in the system, so the clutch is more likely to slip.

If you're after a brand new FCM then I'd go febi, the febi part code is 26141. VW may supply one, but the febi one is high quality, well priced, and it works perfectly for me. Second hand, genuine ones were unreliable in my experience. To swap it, it's two 10mm bolts and two plugs, located on the passenger side chassis rail (on a RHD vehicle). Might be a bit tricky for access on the V6 though.

For a replacement clutch/electromagnet I sourced a good, used compressor complete and swapped over the assembly to my compressor. It saves emptying and refilling the AC system, and is relatively easy to do. You'll need a decent pair of circlip pliers to do the job. 13mm nut on the front of the compressor, then pull the clutch off. One circlip for the pulley, then another for the magnet. I didn't need a puller for either the clutch, or pulley, both pulled off easy enough. Pulley needed a couple of light taps on the edge to bring it forward for the first centimetre then it pulled off easily. Use thread locker when replacing the nut. There is a torque spec but I struggled to hold the pulley and torque the nut properly, so I just sent it home with an impact.
 

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Discussion Starter · #5 ·
Planning to replace condenser, compressor, dryer and expansion valve. Have lock carrier in service position and contemplating whether to do the job myself or go to Air Con shop.

I decided to replace the FCM and also the belt tensioner.

I didn't look at the marks on the tensioner today prior to replacing, but found an old photo showing that it was probably out of tolerance. Wonder if this could have caused the squealing? I won't be able to drive the car for a few weeks so can't check it out.

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