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Old 05-04-2001, 12:17 AM
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Join Date: Mar 2000
Posts: 217
Well, its that time of year again--hot and humid. Todays high here in NYC got up to 90F so I naturally had to try the A/C. To my dismay, the system wasnt really blowing "ice cold" air but rather "cool" air. I decided it was time to do the conversion that everyone here talks about and have the A/C system working 100%. Took it into a shop that was referred by my tech and they quoted me $180 for what the shop foreman said "convert to R134 and fully charge the system". I have never done A/C work on any car so I dont know what actually goes into it, and what the going rates are. Does $180 seem excessive to do a complete conversion or am I getting a bargain? Also, what other things should I have the tech check/replace on the A/C system while having the conversion done?? Other than the blower motor squeeling once in a while everything seems fine. Thanks in advance, for this site is truly remarkable.
1989 300E ("E 300"-Badged)
Monotoned Astral Silver w/ rear lid deck panel
97 Style Replica E420 Rims 205/55/16
Euro Headlights
Clear Corners
94/95 Taillights
Black Grille Insert
Chrome Exhaust Tips
20% Tint
Pioneer Sound system w/ Sub-enclosure and CD-changer
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Old 05-04-2001, 12:41 AM
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JCE JCE is offline
Down to the Wear Bars
Join Date: May 1999
Location: So Kalifornia
Posts: 2,189

Although i am not a tech, I just went through this process on my '87. When mine started running cool instead of cold, the Tech added dye to the r-12 system and had me bring it back after using it for a week. This isolated the leak(s) that needed fixing no matter which R coolant you use. He then captured the r-12, fixed the leaks (fortunately just 2 bad 'O' rings), replaced the receiver/drier and expansion valve, and evacuated the system for most of the day before adding the R-134A. A/C conversion

Cost for my system was under $400. Depending on where your leak is, your conversion could be more, even a lot more, especially if the evaporator, condensor, and/or compressor are involved. Wherever the leak (preferably found with the dye method), the minimum that needs to be replaced during the conversion are the receiver - drier and the expansion valve, and the system should be evacuated for at least a couple of hours.

This is pretty much what i remember from my conversion. There are several good threads on the conversion in the archives as well. My experience with the r134 is that it seems to take a bit longer to get cold, but seems to chill just about as well as the R-12.

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Old 05-04-2001, 01:41 PM
Johnson Chan
Posts: n/a
Unless you are having leaks or some other problem which requires repairs to the AC, I am against converting to R134a.

The reason being is, yes it is cheaper and friendly to the ozone, BUT it does not cool as good as R12. For the Benzs, I am keeping R12 in them as long as I can. I would rather pay more for freon than be sweating inside the car with the "cool" air blowing.

The dealer quoted me around $500.00 to do a total conversion, so a $180.00 (assuming they are using all MB authentic parts and so forth) would be a bargan. Are you sure they dont have some kind of "hidden charge" or did they include the cost of the R124a?
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Old 05-04-2001, 04:24 PM
Super Moderator
Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,315
You need to replace:

drier bottle - $64
expansion valve - $75,
pressure switch ($24),
temp switch ($20)

Then a flush, evac and charge - $60-80 is needed. Throw in two hours' labor for $130 and some ester oil and you're looking at right around $400 to do it right. If you don't do it this way, you will suffer because the system will not cool as well with the R134.

If you plan to keep the car for 2-3 years, this is a worthwhile investment.

My $.02

Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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Old 05-04-2001, 04:36 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
I have converted hundreds of cars to 134, maybe a thousand. Probably a hundred 300Es. BUT I haven't done a pre 1990 300E in almost 2 years. I do not do them if they have the 10p15c or 10pa15c compressors. This is writen on the back head of the compressor. These small compressors do not handle the extra load well; they didn't do great in R12 and they ABSOLUTELY will not do better in R134a. There is an absolute 5% decrease in thermal efficiency with R134a.

If you wish to convert (DON"T do it) fix your system first in R12 till it is cold enough to suit you and then make your decision.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician
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Old 05-04-2001, 05:20 PM
Registered User
Join Date: Feb 2001
Location: jErZeY
Posts: 514
Sorry to interfere with the topic,Where is the expansion valve located? Is it DIY?Thanks

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Old 05-04-2001, 05:50 PM
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Join Date: Apr 2000
Location: Falls Church, VA
Posts: 5,315
It's sort of behind the firewall where the pressure and suction hoses go. I managed to remove and replace mine on the 300E.

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