Ac compressor rattle in old Audi - AC Auto Repair Help Forum


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Ac compressor rattle in old Audi

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capman
New User

Dec 26, 2008, 10:55 AM

Post #1 of 3 (3653 views)

Ac compressor rattle in old Audi	Sign In

84 audi 4000S , 1.8 litre

Took great pains not long ago to totally rebuild AC system as old compressor suffered "black death". All new lines, evaporator, receiver/drier, condenser, expansion valve, and last but not least put on a rebuilt York Mini compressor but used my old clutch. Carefully put in exact amount of oil called for with the compressor and then had rebuilt system charged commercially.
Worked great for about 6 to 8 weeks. Then compressor started rattling, particularly noticeable a low rpms. Thought mounting bolts had loosened so I torqued those back up and it seems to help the first time I did so but it recurred shortly thereafter. I then started thinking belt was maybe loose so I carefully tightened it to spec (.39 inch deflection). Maybe a little better for a few days. Not long after that it started rattling as bad as ever and no amount of tightening of bolts or belt help. Clutch seems to engage smoothly and I see on deviation or wobble as it is turning when engaged.
Thoughts? Cheap rebuilt compressor (Factory Air brand) crapping out? I am pretty sure a refrigerant overcharge can cause rattle but I have put no more refrigerant in it since it was professionally filled.. Can a moderate undercharge do so also? Other ideas?? thanks

Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Dec 26, 2008, 11:44 AM

Post #2 of 3 (3650 views)

Re: Ac compressor rattle in old Audi	Sign In

Ok: Don't wait as you could end up right where you started again!

Yes - low charge COULD do this as it wouldn't carry much oil with the refrigerant as it should. Take pressures and temp observations at once and find the leak. Leaks can happen anytime without any good reason.

Also - Rebuilts and new alike can have failures. This should be under warranty as you did replace the filter/drier which they would call you on.

A maybe: Try spraying some WD-40 on the belt and see if that shuts it completely up for a short while. If so - the belt itself new or not might be the issue! No kidding on that and they can do that with just a certain load or for any reason. Rule that out. If it does respond to WD-40 and is perfect hit back for tricks or more ideas.

Still there? If pressures and performance are right then persue a replacement compressor under warranty before it throws junk thru system again which it will if left unattended. Unplug the clutch so it can't work to prevent further damage as you may be fine with just the compressor right now.

It's unlikely that the clutch is doing this unless the noise is also heard with the compressor OFF.

Side note: Any replacement compressor should be spun with new oil many times before it's charged and operational. There's a period of time if charged while running (most places will only be able to do that way) where it's not full along the way and running dry till you approach fully charged. Severe damage can happen with new/rebuilt units if that's not tended to. The charge carries the oil for continued lubrication.

Act fast - save aggrevation now,

T

capman
New User

Dec 26, 2008, 12:00 PM

Post #3 of 3 (3647 views)

Re: Ac compressor rattle in old Audi	Sign In

thanks. all makes sense. I will try your suggestions. By the way, I did disconnect the compressor clutch. Was afraid I might be headed for another meltdown if not careful.

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