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12V A/C Compressor replacement

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12V A/C Compressor replacement

  #1  
Old 05-08-2012, 01:19 PM
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Default 12V A/C Compressor replacement

Finally getting ready to swap out my A/C compressor, hopefully the last thing I'll need to do before I can drive my car finally. Just wondering if I'll be needing any special tools or if there's anything I might not have thought of thus far.

Thanks, Mike
 
  #2  
Old 05-08-2012, 01:52 PM
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I'm getting ready to do the same exact thing. The A/C compressor clutch had the electromagnet coil burned out when I got the car, the A/C had been blowing plenty cold air just a couple months prior but suddenly stopped. Checking the green wire that goes from teh terminal connection under the hood, down to the compressor itself revealed a good solid 12 volts on the wire when the AC controls were turned on and the compressor clutch should've been engaged and turning, and unhooking the wire and measuring to ground with an ohmmeter revealed infinity ohms.... yep, burned out clutch electromagnet coil.

I bought a brand new Denso compressor off Amazon.com for $288. The cheapest I could find a replacement clutch assembly alone was $200 for this compressor, so I'm replacing the whole unit. You're supposed to replace the receiver/drier cannister anytime you open up refrigerant lines anywhere, but I'm going to skip that. My system is still sealed, and I'll only have the lines opened for a couple minutes and it is not humid here at all (Texas) so no real danger of the dessicant inside the receiver/drier getting water vapor contaminated in the short time. If you have any doubts about that, go ahead and buy a new receiver/drier and replace it at the same time. The instructions that came with the new compressor insist on replacing that part too, but I've replaced enough compressors to know when I can and cannot get by with skipping that part, and since my A4 B5 has only 74K miles, I know the refrig lines and sealed system are still internally in pristine condition.

Since the whole front has to come off the car to get access to the compressor, now's also good time to also perform timing belt replacement (and all the related stuff that goes along with that). Mine was last done at 45K miles, but that was 9 years ago, so I'm doing it too at the same time. (also includes serpentine belt and all idler pulleys, tensioners, water pump, etc, etc, etc). I'm also doing new valve cover gaskets and camshaft seals too, just because I might as well do it all while the front is off the car... altogether, I bought about $1K worth of parts, and will do all the labor myself.

Changing the A/C compressor will only need the usual kinds of mechanics' hand tools for doing engine-related work on an Audi , plus you'll need an R-134 charging kit (manifold gauges, etc), and a refrigeration vacuum pump with all the correct hoses and fittings, to pump down the sealed system to at least negative 28-30 inches of vacuum and verifying no leaks before re-charging it up with R-134 after you're done putting it all back together.

Changing out the timing belt requires a whole set of additional specialized tools for that job, if you're doing that replacement too. See Blauparts.com for pictures of the kinds of tools you need for that.

Might want to check when your timing belt, etc, was last changed, since if you gotta take the front off the car to get to the A/C compressor, you might as well do all this stuff at once like I'm about to do.
 

Last edited by CheckerBird; 05-08-2012 at 02:06 PM.
  #3  
Old 05-08-2012, 04:00 PM
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Awesome advice for anyone reading this. Won't apply to Doc though - he just rebuilt the engine this past year and all the timing parts were done.
 
  #4  
Old 05-08-2012, 06:04 PM
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I just read thru some of Doc's old posts where his engine trashed after only owning the car for a couple days. Ouch.

Sorry if I dredged up any bad memories.

I damaged my A4 the first night I owned it... been driving a Chevy pickup for ten years and coming home the very first night in my A4, turned onto the road in front of my residence crossing a big dip that never bothered me before, and promptly smacked a hole in the oil pan.

Ground clearance in an Audi? NOT!

When I turned into my driveway, a huge puff of oil smoke greeted me billowing out from under the car. I quickly pulled to the end of my driveway and shut off the engine, got out of the car and looked underneath the front bumper to watch the last 2 or 3 quarts of oil drain out onto my driveway Man, I never knew just a couple quarts could make such a huge puddle, but was oh so happy to see plenty still coming out of the hole, knowing that the engine still had plenty enough still circulating in it up to when I turned it off.

Because of that incident, I found these forums and not only located a good place to buy a new oil pan (and an air conditioner compressor too) I also learned about the timing belt issues of Audi engines right here too, else I might have kept driving this car (now has 74.6K original miles) until something in the TB realm broke catastrophically.

BTW, the new oil pan was a lot cheaper than I ever expected ($58 including 3-day shipping) and was a piece of cake to replace.
 

Last edited by CheckerBird; 05-08-2012 at 06:28 PM.
  #5  
Old 05-08-2012, 09:45 PM
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Yeah I managed to get the old one out pretty easily today, gonna put the new one in tomorrow. Got it from a part out, it's in decent shape. Can't afford $300 for the new one right now. Can't even afford the $40 for the cannister.... so I'm just gonna put it all back together and hope for the best. I've never had a vehicle with A/C before... so why start now?! (Plus I'll be in Egypt for the next year so I might as well get used to sweating :-P)

But anyway, I got in there and having gotten a bit rusty in my sloth while awaiting this part I didnt think to drain my radiator and spilled G12 all over the driveway (who likes cats anyway?) Came out fairly easy, 3 bolts or so. Looks like all I'll have to do now will be to wiggle the "new" one into place and connect the wire. Hope I'm not forgetting to do anything...

After that it's install the new battery and align the throttle body: cross my fingers and toes and take it for a drive.
 
  #6  
Old 05-08-2012, 10:52 PM
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In my past experience with auto A/C, as long as you don't leave the drier cannister open to the atmosphere for extended time periods (i.e just long enough to swap out a compressor) and make sure you pull a good vacuum (e.g run the vacuum pump for 30-45 minutes) that generally gets all the moisture out of the drier plenty and sealed system good enough for the A/C to once again make cold air again. I left my old Chevy truck's A/C system open for all winter long after a hole rubbed into one of the aluminum lines, and just used JB-weld to glue the hole shut, pulled a good vacuum on it, and re-charged with R134 and it's blowing icicles out of the vents today

Pulling a good vacuum on the sealed system before re-charging with refrigerant seems to be the primary key to getting A/C performance back to good working condition again. I've never really encountered problems with internal icing n an auto A/C and have worked on many of them from my old hot-rod days of my teens until today.
 
  #7  
Old 05-10-2012, 12:21 PM
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Originally Posted by CheckerBird View Post
In my past experience with auto A/C, as long as you don't leave the drier cannister open to the atmosphere for extended time periods (i.e just long enough to swap out a compressor) and make sure you pull a good vacuum (e.g run the vacuum pump for 30-45 minutes) that generally gets all the moisture out of the drier plenty and sealed system good enough for the A/C to once again make cold air again. I left my old Chevy truck's A/C system open for all winter long after a hole rubbed into one of the aluminum lines, and just used JB-weld to glue the hole shut, pulled a good vacuum on it, and re-charged with R134 and it's blowing icicles out of the vents today

Pulling a good vacuum on the sealed system before re-charging with refrigerant seems to be the primary key to getting A/C performance back to good working condition again. I've never really encountered problems with internal icing n an auto A/C and have worked on many of them from my old hot-rod days of my teens until today.
I've never worked on AC systems to this extent. (insert stupid question....here!) how would I go about pulling vacuum in the system?
 
  #8  
Old 05-10-2012, 02:53 PM
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Pulling a vacuum on an air conditioner system means to connect a set of (refrigeration service tools) manifold gauges and a vacuum pump to the charging ports on the refrigerant lines and pumping all the air out of the system, until it's a
really deep vacuum (at least minus 28 inches of mercury below atmospheric pressure, preferably as close to -30" as you can get, which takes 30-45 minutes) , then closing off the manifold gauge valves and the vacuum pump and waiting for like 20-30 minutes to make sure the vacuum in the sealed system doesn't bleed away, which would indicate a leak somewhere.

Do you have access to the specialized A/C service tools (e.g. manifold gauge and hoses set, vacuum pump, R-134 can tap & hose for the manifold gauge set)?

If not, then it may be a whole lot simpler to just take the car to an air conditioner service shop that can pull the vacuum, check for any leaks, and then fill it with R-134 refrigerant.

Whatever you do, don't just put R-134 into an A/C system that's been opened to the atmosphere and still has air in it. It'll never work right, won't make nearly as cold air as it should and could even possibly damage your new compressor if there's enough water vapour from the atmosphere got into the system to freeze up and make an ice blockage inside the capillary tube. Having "air contamination" inside your sealed refrigeration system is bad.
 

Last edited by CheckerBird; 05-10-2012 at 04:15 PM.
  #9  
Old 07-24-2014, 03:59 AM
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Default A/C problem on 52 plate 1.9tdi 130 a4 b6

Hi all, new here.

I'm after some advice refgarding my air con. The A/C worked perfectly up until a few weeks ago when it suddenly stopped blowing. Yesterday I was able to get under the car and found a bolt and plate was missing from the front of the compressor. Luckily I then found both parts sat in the undertray and reffited. I have come across some posts of others having this problem and when they refitted the plate, their air con worked. Mine doesnt seem to have changed at all though. Can anyone tell me what this plate is for and is there any special way it needs to be fitted/set up?

I have had the system regassed and also havent noticed the A/C fan working if this is any help?

The system has been checked with a VAGCOM and didnt show any faults.

Any help would be much appreciated as its just hit 30c outside!

Thanks in advance
 
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