for the upcoming AC rebuilt, I've been brain wracking on the different refrigerants out there...the cars are built for r-12, which CAN be obtained, then there is r-12 freeze...ai yi yi

well what I do know is that the r-12 will run colder and at lower pressure (the pressure the system was designed for?)

just want to get some insight here


thanks all!

__________________
-SpecialDelivery
1985 300CD Silver/Blue H&R Suspension (Sold, still cryin over that)
1982 300SD Silver/Blue '85 OM617 (Sold)
1982 300D - Blue/Blue (Sold)

In FL, I would suggest that you make the effort to obtain and use R-12.

You won't be pleased with any alternative other than propane/isobutane. That fluid has its own issues, however, at very high ambients.

Im still liking my propane. At $2.00 a can, one can not go wrong.

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1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

Thanks BC, I was thinking that also. Someone cautioned me about getting the temp (too low) that it would cause the evaporator to freeze up. Any thoughts on this?

__________________
-SpecialDelivery
1985 300CD Silver/Blue H&R Suspension (Sold, still cryin over that)
1982 300SD Silver/Blue '85 OM617 (Sold)
1982 300D - Blue/Blue (Sold)

You filled with just propane? I tried that on my 92 Jetta... the air was ICE COLD. I mean... unbelievably cold. 40* vent temp on an humid 101*day, water pouring out of the evaporator drain. Stepping in and out of the car gave me a headache. But the high side pressures were way too high, approaching 300 PSI.

What pressures are you seeing?


On the topic of evap freeze up... that should be impossible on an old Benz. They cycle the compressor based on evap temp, when it gets too cold it shuts the compressor off.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

The evap has a temperature switch that cycles the compressor to prevent freeze up. It's the only thing that controls the compressor. Many times this switch is set a bit too high and the discharge air temperature is close to 50F. This, I believe, is a fundamental problem with many of these vehicles.

The SDL has a non-functional evap temp switch and the evap can get down to 28F. on R-134. Of course, it will freeze in this scenario. However, if the ambient temp is 90 or above, the evap doesn't quite get down to 32F. and the discharge air remains below 40F. If the switch is working, it would cycle the compressor and the discharge air would climb to nearly 50F. There is a world of difference between 40F. and 50F. and that damn switch is the culprit.

Ever have the propane system in ambients of 100F or more? What's the result?

I agree, but it's not legal in Fl. Then again, who's going to know unless you spill the beans.

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82 300SD 202K
82 300SD 233K
83 300TD 340K
82 300TD 98k euro (parts on the hoof)
85 300TD 282K
83 300TD 197K

Crazy high high side pressures.

-J

__________________
1991 350SDL. 230,000 miles (new motor @ 150,000). Blown head gasket

Tesla Model 3. 205,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.

Yep, the system doesn't do well unless the ambients are not more than 95F or so. Supposedly, the addition of isobutane to the mix helps with that situation.

I'd like to try it up here, but I certainly wouldn't do it in FL.

EPA recently changed the rules, ca. 2011:

Choosing and Using Alternative Refrigerants for Motor Vehicle Air Conditioning | Alternatives / SNAP | US EPA

E.g. Freeze 12, FRIGC FR-12 are approved; Duracool 12a is not approved. Propane is not on the list by name, but is probably considered a "flammable blend of hydrocarbons."

Never had it over 100 F, so cant say. I am not even sure if its straight up propane. Its a camper size little thing. 2lb size maybe? It may be a blend.

All I know is R12 is hard to get, this was not and after reading many, many thread here and other places on it I decided to give it a try.

This summer I will be replacing all the o-rings and vacuuming the system and filling up again.

__________________
1991 560 SEL / 185k miles
1992 750il / 17k miles - project car

The 240D has been "converted" (very cheaply and poorly) to R134a but it's the only one that doesn't leak. Our "average" summer day is 82-88 and we have about one miserable month of 90-92. Up to about 80 ambient, it cools as well as I'd like it to. Beyond that, it warms up considerably but it's still better than having nothing.

Before its compressor died, Freeze 12 used to perform almost as poorly but ever so slightly better in my 300SDL.

The 300SD has a working system but it leaks so fast that 3 cans of R134a are gone in less than 10 days. Have about quit trying to mess with it.

Best thing I ever did was move to the mtns... 2 hours away, 2,000 feet higher, and summers became a whole lot better with just 4-60 air conditioning.

(Though with w126 window regulators being what they are, it's usually more like 2-60 at any given time in at least one of the two of the silly things)

__________________


~Michael S.~
Past cars:

1986 300SDL
1987 300SDL
1982 240D
1982 300SD


Current:

1987 300SDL

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John

ya ought to bring that SD down to me, and let me fix the leaks!

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!