AC compressor?

[Blade74]

So I've had the alternator go in my car around October last year.
I replaced it and the fan belt at the same time.
I also asked the mechanic to let me know if I should change any other pulleys or water pump etc at the same time due to it being at about 100k kms and also approx 7-8 years old.
They said no it's all fine.
About 2-3 months later the belt came off whilst driving and partially wrapped around the viscous fan.
I took it to the dealer instead of local specialist who did the original work due to proximity and also having lost a bit of faith in their work.
The dealer put a new belt on and replaced a pulley.
They said the viscous fan seemed fine but sometimes when a belt comes off and wraps around it can get damaged.

Prior to the initial alternator going I would occasionally get a thumping noise similar to what a water pump or concrete pump in a high rise building would make when I first started the car. It generally would go away after the engine was warm and I'd driven it for 15 mins. It would also instantly go away if I turned the AC off.
I now also get a weird purring sound when I first start my car that also tends to go away when it warms up. It sounds like a purring noise and comes and goes every few seconds.
Im assuming it may be the AC compressor or maybe viscous fan.
Any ideas on what tends to go and or experience with similar issues?

[kg74]

First if you think it is your fan - take it off and run the car shortly (don't overheat it) to see if the noise goes away.

Based on the description you provided your clutch may be failing. The noise is when the compressor engages. You can take off the belt and spin it to check the bearing.

One possibility is that the gap on the compressor clutch may be too great - not sure if this can be adjusted. On some cars one can remove some shims to get it back into spec.

If the compressor is still operational it can be rebuilt - not that hard and plenty of videos on it. I am not sure what the cost of the clutch assembly is - but I would imagine the parts are available - you may have to cross reference to find them.

My guess is the compressor bearings are starting to fail. I would get this fixed before it completely goes and takes out the rest of the compressor. You should be able to just remove the compressor clutch and swap out only the bearing. Usually they are a common bearing and easy to find - if you can be down a bit pull it off and bring the bearing in for a replacement.

My RR is in the shop right now or I would go and look, but I think you may be able to pull the clutch with the unit still in the car. Not sure on the space. Do some more research and testing, but if it is the bearing you may be able to find the right size and have it all done pretty quick.