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Old 05-22-2003, 03:29 PM
Thomaspin's Avatar
Join Date: Jun 2001
Location: CA
Posts: 531
Air conditioning repair - illustrated

Just in time for summer.

I don't cover compressor repair here - maybe later - but cover most of the other components. I also replaced the expansion valve, but did not illustrate that - the bad language might have shown. It is quite inaccessible!

Nor do I get into R12 vs. R134a vs. others - you choose. Mine is R134a.

Go to my web site - Cars - Technical - Chassis.

Enjoy, and keep cool!
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Old 05-22-2003, 03:56 PM
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Join Date: Aug 2001
Location: secret
Posts: 3,044

Taking time to document things like that take a special talent and dedication. I have seen Haynes repair manuals that weren't near as good as that! You have my respect for doing things like that and sharing them. I would like to document my work like that, but there would be beer cans visible in some (if not all) of the pictures!!
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Old 05-22-2003, 05:03 PM
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Join Date: Feb 2003
Location: Houston, TX
Posts: 16
Repairs - illustrated


Your website is outstanding. I really enjoyed reviewing it and plan to use it whenever I take on any one of the repairs you describe. One question: Do you know any other sites that give the practical kind of instructions/directions that yours does? (especially for diesels, thats what I own).

Keep up the good work,

02 E320 (replacment)
85 300D (Blue, wrecked)
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Old 05-22-2003, 06:33 PM
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Join Date: Dec 2001
Posts: 571

Another very nice job. Thanks for taking the time.
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Old 05-22-2003, 07:31 PM
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Join Date: Sep 2000
Location: Shalimar, FL
Posts: 79
Thomas, I asked the same question about your figures in another A/C post where you stated you used 1lb 8oz of R-134 and did not receive an answer. Mercedes shows the 300SD capacity at 1.5Kg of R-12, since R-134 is usually charged at approximately 80% of R-12 you should have used about 40-42oz, this is twice as much as you stated on your webpage. I cant see how the car cooled with a 20oz charge, also how cold is where you live if you call 40F water warm, here in North Florida thats frostbite temperature.

Bob H.
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Old 05-23-2003, 09:59 AM
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Join Date: Jun 2001
Location: CA
Posts: 531
Thanks, all...

...for the nice compliments. I, too, would love to learn of other sites with similar procedures and illustrations!

Roberth58 - thanks for pointing out my error on the water bath temperature - that should, of course, be 40C not 40F - I went back and changed the slide. The weight used is correct. The system cools as well as when it was new.
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Old 05-23-2003, 10:16 AM
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Posts: 613

I also have a section on AC upgrade/repair, although that particular section is not documented as well as others.
1993 500E
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Old 05-24-2003, 10:30 AM
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Join Date: Oct 2001
Location: around Charlotte NC
Posts: 573
happy with guages?


Great site and documentation. As posted in another thread I'm getting ready to replace my compressor in about 2 weeks. A good friend will assist me and has been doing A/C for 20+ years. At our last attempt at working on an A/C system he was grumbling about his sticky old guages. The vacuum gauge would sometimes stick and not show a true reading. So I'm looking for a set of guages to give him as a thank-you for his many efforts.

Are you happy with the guages shown in your pictures? Anyone else have a recommendation?

I think I have the shopping list ready for the compressor replacement. New compressor, r/d, lots of flush, the o-ring kit to replenish my friend's supply. I'll check the A/C relay and other electricals this week-end as well to get ready.

A question to the general population... is there any special o-ring or gasket needed between the compressor (nippondenso ) and the manifold?

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Old 05-24-2003, 11:44 AM
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Join Date: Jun 2001
Location: CA
Posts: 531

Thanks for the kind words.

Those Yellow Jacket gauges work very well, but I cannot objectively analyze their longevity as I bought them some 5 years ago and they sat unused, waiting for the a/c to fail. Once it did, I was motivated to learn all about a/c work. Thus they have been used only a handful of times.

Are they accurate? Well, the instructions for the venturi vacuum device I illustrate state that it should generate 29" of vacuum, which is exactly what my gauge shows. Plus, the pressure readings vs. weight of refrigerant in the system correlate well, so that's some comfort they are reasonably accurate. And, as I know to my cost, they instantly show a leak. (My condenser blew and the gauges immediately confirmed a vacuum leak - I couldn't get anywhere near 29 inches of vacuum).

I can't find this brand sold as a set on the web, but I would think any of the sets sold by would be a good alternative - the company specializes in a/c. The leak detection kit they sell (see my web site) is very useful, too. For occasional use, I would go with the least expensive set. Don't trust their web site if you need them fast - call and check they have your item in stock first. I waited an inordinate length of time for the Mastercool a/c book, as they took my money without the item in stock. The book is exceptionally useful, despite the focus on US cars. Most of the a/c components in my W126 cars seem US made, and many of the fittings are non-metric.

By way of reference, I seem to recall I paid under $100 for the yellow Jacket gauges - they are calibrated for R12, R134a, R22 and some other R.

Don't forget to add beer to your shopping list. A dog helps too when you need a break to relieve frustration.
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Old 05-24-2003, 05:18 PM
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Location: Santa Monica, CA
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Thomas, Thanks, as always, for such a fine contribution to the rest of us.

Either of the top two gauge sets by Mastercool makes a thoughtful gift:
The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)
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Old 05-24-2003, 05:55 PM
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Join Date: Oct 2001
Location: around Charlotte NC
Posts: 573


Thanks for the input. My buddy does a heap of car work and A/C work as a side business. In fact when he was first starting work as a teacher 25 years ago in Ft. Worth, he made more money in the 3 months in the summer doing mechanical and body work than he did in the 9 months as a teacher. His 20 year old guages are just worn out I think from use. He is currently disabled and supporting himself off odd-jobs. I owe him a least this favor and want to find something he can use for a while.

I'll take a look at the suggestions and probably head toward the higher end. Oh yeah, and remember the beer too!

I also really appreciate the thought and consideration given by the members of this forum to assist each other. I'll let you know the progress in a couple of weeks.

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Old 06-23-2003, 11:36 AM
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Join Date: Jun 2001
Location: CA
Posts: 531
Twin auxiliary fan caution

Having just done the job once more, this time on my twin auxiliary fan 1990 560SEL, I would warn anyone contemplating the job of condenser replacement that it is much more difficult on the twin-fan equipped cars.

Accordingly, I have adde a a few words of caution to my illustrated web site piece.
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Old 06-23-2003, 12:58 PM
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Outstanding work on your website!

I am writing to join the list of people thanking you for your documenting your work. Your record keeping certainly delayed the completion of your work, but has given all who will avail themselves an enormous service. Bravo!
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Old 06-23-2003, 01:43 PM
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Join Date: Mar 2001
Posts: 51
Thomas: I always enjoy your work, and this is another excellent addition to your site. Kudos!

Just a couple of suggestions for you to consider. First, on slide 26 you state the engine should be turned using a 22mm wrench on the "water pump"--I believe this is a typo and you meant to say the "power steering pump" (which is what your picture illustrates). Secondly, in slide 63 where you discuss the charging procedure, you may want to state the obvious and tell the reader to "Start the engine and engage the AC system at Max cooling". Don't laugh--I could tell you stories...

Keep up the good work, my friend! John Downey
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Old 06-23-2003, 01:59 PM
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Join Date: Apr 2001
Location: Jacksonville Florida
Posts: 723
Great Job...Looks like The Micro film from Mercedes...
Thank you for the Great Job! Im Sure your site WILL Help Lots of People!

Last edited by mark cummins; 06-23-2003 at 02:58 PM.
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