Too much refrigerant?

[mgmarsh39]

Hey guys,

Had a new a/c compressor installed during my timing belt job due to a bad clutch. When I picked the car up, the compressor was making noise when engaging etc, so my mech took it back, made adjustments and viola it was good!

Fast forward to now, rather than PA (where it was like 45-60*) I am now in TX, where it's like 105 today :/... The a/c works great in the morning and evening, however during the hottest time of day, it never really gets cold enough. I suspect the system has too much refrigerant. What do you guys think? I will be dropping it off at a local shop to diagnose, but wanted to get your opinions.

Thanks!

[hahnmgh63]

A good A/C shop should be able to figure it out, pretty simple system. Hopefully they put a vacuum on the system before they filled it after replacing the compressor. Standard temp/refrigerant pressure tables apply as the manual only calls for a liquid fill by weight so start with system pressure to begin with. If that doesn't work you may need a complete evacuation and refill, couldn't hurt to install a new receiver/drier/filter while you're in there if it was opened for long.

[mgmarsh39]

Thanks hahnmgh63. Was going to run it over by the local Audi dealer and have them diagnose it.

From what I recall, he did vacuum the system (had that cart of a thing hooked up to it). The problem with the noise was "too much oil in the system", which leads me to believe it is still "overfilled".

[lswing]

TX is a unique level I called hot as sh!t...my car blows cold air in a normal state...but with the black leather inside and total heat the AC could never keep up on a hot day...old and not as strong as newer AC was my guess.

[lswing]

Thanks hahnmgh63. Was going to run it over by the local Audi dealer and have them diagnose it.

From what I recall, he did vacuum the system (had that cart of a thing hooked up to it). The problem with the noise was "too much oil in the system", which leads me to believe it is still "overfilled".

No, especially not Audi of Austin...go to Brink Motorsports in Austin. Or find the user on here with a shop in Waco. I was in Temple...

This guy knows his stuff...http://www.rs6.com/showthread.php/32...econd-hand-RS6

[mgmarsh39]

No, especially not Audi of Austin...go to Brink Motorsports in Austin. Or find the user on here with a shop in Waco. I was in Temple...

This guy knows his stuff...http://www.rs6.com/showthread.php/32...econd-hand-RS6

I'm actually in the DFW metropolitan area, so heading to DFW Audi. The local shops aren't open on Saturday, or I would pop in one of those.

[mgmarsh39]

The new compressor has been eating itself... They found metal shavings in the refrigerant. An Audi part was used, but was done by an independent shop, any hope on getting this warrantied?? Ugh... Audi quoted $6k.

They also said only 1 fan is running, and the fan switch (I think she said) is bad.

***Update***

Ok, so apparently the shop in PA didn't replace the dryer, which they suspect is why the metal shavings are there. With that said, they are charging the system back up and giving me the car back.

Any chance the fan issue is something I can tackle? One is working, but is on its way out. The switch is bad, which killed the other...

[lswing]

Everything is $6k at the Audi dealer. Waco's an hour south, drive it down and have it fixed up. Personally if it's a daily driver, Texas heat is brutal, I'd sell it ASAP...along with lack of quality Audi mechanics.

[mgmarsh39]

Everything is $6k at the Audi dealer. Waco's an hour south, drive it down and have it fixed up. Personally if it's a daily driver, Texas heat is brutal, I'd sell it ASAP...along with lack of quality Audi mechanics.

Selling it would be quitting! LOL

So after talking with the tech, the compressor is actually fine. He said he found some debris in the restrictor valve? Anyway... he recharged the system and it seems to be working much better than before. He did say it was slightly low on refrigerant. If there is debris in the system, won't the dryer catch it?

So, the driver's side aux fan is not running. Per lswing the heat here is brutal so I need to get that done. Any chance one of you guys did this job and can share your experience?

[marklar182]

If someone was in the engine bay working, first I would check the connections. If they are OK you need to test if it is the fan or the Controller. (controller is on the drivers frame rail)

To replace the fan you will have to put the car in service position.

[G2]

It may be over filled which will cause low performance, but if too low, A/C will cut out at lower temps since pressures are less. Most shops use generic R134 that is lower performance. Avoid it. It makes a big difference in Audi's.

Obviously the fans need to work. When hot they will run fast. The A6/S6 has a 3rd fan to help blow thru the condensor- those can be VERY loud. Removing the under tray during summer will help (or "modding" it). Be sure your engine ECT is appropriate; use a scanner to verify while driving in all conditions.

The debris is not from anything other than from the first compressor. Likely due to low or incorrect oil charge and/or a lot of run time. Oil wears out. Or incorrect pressure differentials (read: restriction), and therefore more compressor stress. The system must be flushed out and all serviceable parts replaced (expansion valve, dryer). The condensor will benefit from a thorough cleaning. I spent 2hrs washing the one in my B7A4....and picking out debris.

A/C's should get an oil change every handful of years, ideally. In reality it's hard to do. I usually add more oil than spec to help longevity. Performance is not compromised if pressures are adjusted per conditions (I use weight as a rough guideline- one weight does not fit all...) I've had some vehicles output 26F in hot weather just running in the shop. That's frost blowing out...

Some well known AC flush agents are absolute waste of money. And no matter how much is used will continue the saga of failures.

Someone with extensive German car experience should be the only person servicing the AC system on this car. Hopefully an RS6 tech/wrench/owner like myself, but that's a tall order on our 13yr old cars.

A/C systems are fundamentally simple, but there's a lot of grey area to work with to make things better.

[mgmarsh39]

Great info thanks G2.

As stated earlier, when the shop in PA replaced the compressor it was making a loud humming noise and vibrating the car. The mechanic said it was due to too much oil, adjusted it and gave it back working fine. Wondering if that may have caused the debris. The AC seems to be working well now, so I guess I will just keep driving until it stops :/.

The Aux fan is next on the list.

[mgmarsh39]

As a update, the smaller aux fan is dead and so is the module. Steve over at Zinkwerks has ordered both fans and the module. Hopefully this will take care of the problem!