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Post Info TOPIC: Recent 560SEC work


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Recent 560SEC work


  • Retrofit FROM previously retrofitted R134a BACK to the much better R-12 (the car was retrofitted to 134a when I bought it 10 years ago; worked like shit here in Texas with 134a).  New Denso compressor, expansion valve (PITA to get at), drier, high and low A/C switches, and about 2.5 pounds of Freon with a dye pack thrown in for good measure. Drove Houston to Austin and back today (nearly 400 miles round trip); A/C nearly froze me out of the car.
  • Replace totally disintegrated foam condensation drain hose on driver's side (common overlooked issue on the 126)
  • New brake fluid reservoir (seal on top started leaking when power-bleeding, so decided to just replace it)
  • New motor mounts and transmission mount (old ones had 70K miles on them; driver's side mount totally broken)
  • Replaced stripped motor mount allen bolt with one from my stash....

Enjoy photos....



-- Edited by gerryvz on Thursday 27th of September 2012 09:43:12 PM

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The compressor came new with PAG oil already in it, so it had to be drained and disposed of. I used a professional-grade Snap-on system for vacuuming and measuring new Freon into the system. Everything was done correctly and to a "T". The system was vacuumed out for several hours and thoroughly flushed. The last thing I'd want to do is to contaminate all this new gear with residual PAG oil in the system....

A system that was designed for R-12 just isn't going to run the higher pressures and such that would be required of an R-134a system. My later Benzes (1994 and 1995 models), which were designed from the factory to run R134a, operate just fine here in Texas, but even then aren't QUITE as efficient as an R-12 system. Also the condensors that are designed for an R-12 system using R134a just isn't going to be as efficient as a "parallel-flow" condenser that is designed for R134a.  An R134a system designed from the ground up to run that refrigerant, is going to be just as good as an original R-12 system. I still think that R-12 works best in humid climates, though.

My home's two A/C units run R-22, which is the commercial/residential analogue of R-12. They're requiring R410a for all new residential installations, but A/C units tend to run $10K each and up, so I'll only replace mine when I HAVE to. I just spent $3,500 on new evaporator coils in my attic for my downstairs unit, this spring. So I'm in no hurry to replace any A/C units. R-22 I believe is still actively produced. It can be used to replace R-12 in a car, in a pinch....

R-12 is still produced in Mexico, new. However, there are PLENTY of current stocks of R-12 that is new and sitting in warehouses, to last many decades into the future. Not to mention reclaimed R-12. My A/C guy had a 30-pound can of R-12 he'd only used once, sitting in the corner of his garage for the past 15 years. He didn't need it so he gave it to me for a real song. You'll see commercial prices on R-12 anywhere from $40 to $80 a pound, depending on markup. I believe R134a tends to run around $25-30 a pound, but I could be wrong on that. I used to pay about $10 a pound for it years ago, but the price has gone up substantially as the price of R-12 has come down due to lack of demand. These days, it's only incrementally more expensive to run R-12 than it is to run R134a. Another reason why I retro-fitted BACK to R-12.

Now they're trying to replace R134a though. Mercedes just issued a press release this week giving the automotive industry a big "F U" because they found that the new refrigerant is highly flammable in the instance of a car crash, so they said they're sticking with R134a. Let the Fords of the world create another exploding Pinto with flammable refrigerant.

See attached press release.




-- Edited by gerryvz on Friday 28th of September 2012 11:23:14 PM

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R134a.pdf (111.5 kb)
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Cool!

Nothing feels better than a job done well.



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I'm sure PowerStroker will fault me for a job NOT well done because I was wearing protective gloves, so not getting grease under my (non-self-made) fingernails, like he does. LOL !

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No, I really have no issue with it so long as you didn't vent any refrigerant to the atmosphere in your process.

I'm just curious if R12 really works that much better than R134A? Both of my vehicles use R134A and even up here in MN we can hit triple digits in the summer, yet I have been satisfied with the cooling capability of both vehicles. It's been about a decade since I've even worked on an R12 system, and my current dealership doesn't even have a working R12 recharge machine. Probably because the salt they use on the roads in the winter here has already consumed any vehicle old enough to still use R12.

I know R12 isn't produced anymore, so they can only sell remaining stock. What's the current price for a pound of R12 these days anyway?

Oh yeah, and what did you do with the oil in the system? I hope you flushed the lines and heat exchangers properly. You do realize R12 systems run mineral oil for compressor lube, and R134A systems run Polyalkyeine Glycol... And they don't mix well without destroying rubber components. Why do I get the feeling you're going to be in there again soon???

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I have had sucess with both R134 and R12...

The only diffrence being that head pressures using 134a @ the suggested 2+ pounds results in some scary high numbers. I have worked around this by putting in a tad less than 2 lbs.

You can now buy evaporators for the W126 with 134a fittings, so if someone wants to squeek by on the cheap I'll put them into an R134a retrofit, if they have deep pockets Ill lay the R12 on them. 



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Yo guys,

All the responses above are correct and true, ( I actually worked as a mobile A/C technician around all of Melbourne repairing & regassing all makes of cars !), and I think it would be fair to say that the use of the correct type and especially the amount of gas for the designed system does work the most efficiently. R12 retrofits to R134A do work ok, but as already mentioned, higher discharge pressures are present at the condenser, and probably the bottom line is that your maybe at best going to get about 6 degrees on the thermometer out of the centre vent with the fan on speed 4 (read maximum), where an R12 gassed system will give you anywhere from 1-4 degrees c, depending on vehicle make and everything else in sound working order...eg. - the heater valve is fully closed etc and the "recirculation" vent setting works !
The biggest problem with the retrofit we've found here "down under" was shut-down of the system from the HP switch on the hottest days. The best results we could get was to charge the system with the minimum required amount of gas, and this problem resolved itself, though the vent temperature was a little higher at about 8 degrees c. I think Power-stroker mentioned the use of particular oil types for different systems, and this is / was true, as our company found a supplier of a synthetic oil that ensured compatability with all gasses and compressor types, and well, so far so good ?...
Appart from collision damage, the only leaks that you'll generally ever find will be from the front seal on the compressor, or 'o'ring failure normally at the compressor hose mount. The hoses will fail also in the crimped fittings due to torque movement back and forth of the engine from normal running, and if they're allowed to rub through on something. I've found that if you have to replace a pair of 'o'rings at the compressor hose-mount, all the other 'o'rings should be replaced in the system as a matter of course, and as Power-Stroker mentioned, the suitable ones should be used with the gas type selected. It's always good to coat them with refrigerant oil before fitting, and while your at it, a new Reciever Drier is a must. If your not sure about gas quantity in the system, and your only "topping up" due to a customers insistance....a "little whisp of bubbles" like what you see rising in a glass of champagne when seen at the reciever-drier sight-glass is a fair approximation to reasonable operation...Hoping that I haven't said too much or steerd you wrong !!!

Cheers,

Rastus

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