Paulsome

Hi all, new to the site (and Audis in general). I picked up a 2005 A4 B6 with the 1.8L back in the winter. Love the car so far, but I recently tried the AC and the ECON mode stays on. From the research I've done it seems this can be caused by a bunch of reasons, and that a scan tool is basically the first step to figuring out more specifics as to why the AC won't kick on. I have access to an OBDII reader tool, but it will only diagnose faults that cause a check engine light. I've seen other posts refer to a VAG-COM cable/tool that can read AC fault codes as well, but a Google search for this sort of goes down the rabbit hole - some specify what cars they work with, some don't. Some don't even specify Audi...

So firstly, does anyone know what specific tool will be compatible with this generation of A4 and can read AC codes? Or have a link to one that they like/know works? Not against spending a little bit of money (within reason) if it can also read other codes for the drive train, emissions etc.

My plan in the meantime is to hook up a pressure gauge to the high/low ports to see what the static pressure is to see if I have any obvious leaks in the lines. Also double checked the fuses, both seem to be fine.

Thanks for any info you can provide!

lyleswk

I would start with the most likely which is low freon.

Aside from that, you would need a VAGCOM tool that reads VAG codes if it is something deeper than that. I got mine here: https://store.ross-tech.com/shop/cat/VCDS. Note there is also a free limited capability software that runs on a laptop.

Paulsome

Thanks for the link. Did you get one of the enthusiast tools, or the professional? I couldn't find on their website which types of codes each unit will read to confirm AC codes, but I'm hoping the enthusiast one will do the trick since it's more in my price range.

My thought was to add refrigerant as well, but my understanding of the refrigerant recharge kits is that the AC needs to be on during the recharge process. ECON mode means the car has disabled the AC (in this case due to a yet-to-be determined issue), and therefore is not on - just the fan is blowing, right? If so, does that mean that the recharge kit will not work as designed since the AC is not able to run?

lyleswk

I just got the enthusiast. I believe they all read the codes, but the professional allows you to changes settings, log engine or sensor performance, etc. Mine has a module for the HVAC, I just have not ever run it since I haven't had issues, other than recharging the freon.

Paulsome

So a quick update - I ended up taking it into the shop for a diagnostic, and it turns out the compressor is shot. Has anyone successfully done a compressor swap on their car? I was able to find a decently priced compressor online, but the fact that it's buried at the bottom of the engine seems like it's going to be a real pain to get good access to it, even once I remove the plastic cover from the underside of the car. Basically trying to figure out the savings to hassle ratio I'm looking at if I try to fix this myself.

lyleswk

Well, that's not good. Did they tell you the failure mode? Usually, failed compressors blow all sorts of metal particles into the system requiring other components to be swapped like the drier, the expansion valve and condenser. I would check on that first and maybe even get a second opinion.

I haven't looked at the compressor, but know the condenser will require the front of the car be put "in the service position". It basically takes the front of the car off which will allow easy access to the compressor.. Take a look at the links below:

Remove headlights by following the tutorial here on A4mods.com:
http://a4mods.com/index.php?page=web...earcorner.html

Follow Martini's guide to removing the front bumper here:
http://a4mods.com/index.php?page=web...erremoval.html

turbo510

I basically do everything that comes up on my 3.0 B6, except for the compressor change; I left that to a shop that I trust because of the amount of equipment required to do it right. As lyleswk said, if the compressor failure was such that debris got into the system, then it needs to be flushed and the expansion orifice needs to be cleaned out or replaced. The other issue is compressor quality; I had the shop install an OEM Sankyo, not a Chinese copy. All things considered, I was fine with paying $1,200 and having cold AC again.

Paulsome

Yeah, those are good points. I had found a video on how to remove the compressor, and it seemed like access actually wouldn't be the worst thing, provided the car was lifted up. But like you mentioned, I'd have no way of knowing the extent of how much the system needed to be flushed and what other components might have been affected. On top of that, I don't have the tools to properly vacuum out the moisture from the system once the new compressor was in.

I ended up having the shop do the work. I know it's not the ideal conclusion, especially on a forum, where most people are reading these threads to figure out how to avoid the shop in the first place. But my lack of experience in AC systems, coupled with the fact that it was going to be pushing 100 degrees here in upstate NY, I figured it was worth spending the money. Plus the new compressor at least comes with a (limited) warranty, so I guess that's a plus.

Anyway, now the car is back to normal, and I'm looking forward to hopefully many years of enjoyable driving. Thanks for the help, everyone. I'm sure I'll be back the next time something fails!

turbo510

That's good news, you will be comfortable driving your A4! I actually worked at Mazda's California R&D center, specifically on AC system improvement in the 80's, and installed plenty of them, but still didn't want to deal with all that on my car.