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85 Audi sitting for 6 years...system draws down and holds...advice.

Dubbinchris on Wed July 28, 2010 2:45 AM User is offline

Year: 1985
Make: Audi
Model: Quattro
Engine Size: 2.2 L
Refrigerant Type: R-12
Country of Origin: United States

As the title states. I picked up this Audi two months ago. It has an unconverted R12 system and the car has been sitting for 6 years. I have a 2 stage vacuum pump and a set of gauges albeit they aren't they aren't the greatest. As far as I know the system worked when parked. I unscrewed the cap to the low side and for a moment pushed in the valve. It had a small hiss to it so I guess the system had a little pressure in it. I then hooked up the low side gauge and my pump. I vacuumed it down for 30 min to a vacuum of 28. I then closed the valve and shut off the pump. The gauge didn't budge for 30 min. I'm a fairly new A/C diy'er so I'm still learning so I'd like a little advice as to what to do next. I've leaned some through this site and I know there are lots of knowledgable people here. Also on someones recommendation I went ahead and took the test and got my little card to buy R-12. I'm wondering if I should just vacuum it down for a few hours and go ahead and charge the system with R-12 or if there is more I should to do check or clean things out? Obviously R12 is pricey so I'd hate to just throw it in there just to "see what happens". I'm guessing that the fact that it had a little residual pressure in it tells me that it's likely contaminate free. Please correct me if I'm wrong.

Anyway thanks in advance for any advice on this system. I want to make sure I do this properly. Also please let me know if any more information is required.

Thanks,
Chris

bohica2xo on Wed July 28, 2010 3:13 AM User is offline

Yes, the system with remaining pressure indicates it is fairly tight after 6 years.

Which compressor is on that Audi? They used several in those years... And much like your other car the charts have big holes in them.

The compressor will determine your next move. The system should be fairly easy to bring back up.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Dubbinchris on Wed July 28, 2010 3:31 AM User is offline

My research tells me it's the mini york, which appears to not have been used in too many models.
It's pretty tight in the engine bay so it's tough to get a real good visual on it to confirm what my inter-web research tells me.

Yeah I have a thing for the oddball cars...lol

Edited: Wed July 28, 2010 at 3:32 AM by Dubbinchris

Dubbinchris on Wed July 28, 2010 3:33 AM User is offline

Just a interesting FYI. Only 73 of this model year were sold in the US and it was the last year the car was even offered here.

bohica2xo on Wed July 28, 2010 4:01 AM User is offline

Ok, easy enough to sort that out.

Service Manual for York compressors. That link is a pdf file. It includes both the standard & mini units, with pictures.

A few pages down that document, you will find a drawing for a dip stick. Along with a chart that describes the various compressor orientations & oil levels.

Since you have the system empty, I would start with checking the oil level in the compressor. I would also add the recommended dose of dye, along with any oil it might need. If the oil level checks ok without adding, that is a good sign.

Personally I would replace the dryer. It is at a minimum 6 years old. It is probably a really common (cheap) unit that looks sort of Like THIS.

Check the oil. Add dye. Replace dryer. Pull vacuum. Check for leakdown. If it is still sealed, charge it back up - with R12 of course.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

Dubbinchris on Wed July 28, 2010 4:21 AM User is offline

Bohico, thanks for the tips. I have found the drier in a few locations. Are four season or spectra decent brands? The one for this car looks a little different than the one you had a link for. I found the four seasons one as cheap as $13. My typical german auto parts site has one for $20 and they are pretty good at making sure they list the correct parts. I'd post a link, but IIRC that forbid on this site. Anyway it will prob be a few weeks before I get to it all, but I wanted to make sure I was armed with a basic plan before diving in. I'm sure I can dig up the info on the oil, and amount of R-12 as well as make myself a niftly little dipstick to check the oil (thanks for that service manual link BTW), but where would/could I dig up info on the proper amount of dye? Are we speaking of something that makes leaks really obvious to the naked eye or something that would require some type of UV light to illuminate it?

Thanks again,

Chris

mk378 on Wed July 28, 2010 9:15 AM User is offline

Especially since you have time, pressure test with nitrogen first. Leaking all the way to basically zero pressure, even if it takes years, is a noticeable leak. I'd also change the o-rings at both ends of the discharge line, this line is the hottest part of the system and it is very common for the o-rings to become hardened due to the heat and leak.

bohica2xo on Wed July 28, 2010 1:49 PM User is offline

The dye is both visible and highly reactive to UV light. The proper amount is covered on the bottle, usually .25 ounces or less. If you buy it from the site sponsor, you get a bottle with enough dye for 3 systems. Use the minimum recommended, this is really concentrated. Be careful putting it in the system, if you spill it you will be looking for a leak that does not exist...

In the shade, or at night it does not take much UV to make it glow. You can use a "black lite" CFL bulb in your drop light.

A nitrogen pressure check will not tell you much at this point. It held some positive pressure, and that may have been what was left of the original charge from 1985. It holds vacuum, so it does not have any gross leaks. You don't own a leak sniffer, so static testing with N2 + 134a is out. Unless you already own the N2 equipment & a sniffer, the cost of the R12 to fill a small system like this is less that the cost of the equipment. The dye & refrigerant in circulation will find any leaks.

If there are any O rings in the discharge I would be inclined to change them as 378 has pointed out. With a mini-york this sounds like an old ARA system, and probably has clamped hoses...

Whatever dryer fits with your system is fine. Even at 20 bucks it is cheap insurance.

Given a choice between two 80's vintage Audi's and scabies - I think I would rather have scabies. But everybody has their weaknesses, and I have owned a bunch of SAAB's... Good luck with your projects.

B.

-------------------------
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.

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