After reading the preceding flame war, I'm a little hesitant to post, but here goes...

I have an inadequately cooling system in my 85 W126 which the previous owner had professionally converted 9 years ago from R12 to R134A. I'll spare you the details, but I have checked blend flaps, refrigerant charge, aux cooling fan, high/low pressures, etc. and everything is in check, but it's just not as cold as an R12 system. at about 95 degrees ambient, I get 58 degrees at the vent when moving, and about 70 degrees when idling. I do a lot of stop-and-go driving and this just isn't cutting it. And if anyone opens a door and lets some hot air in, it might be another half hour before it's cool again. On the highway the performance is much better, but again on a 95 degree day I would just call it "adequate" for the front-seat passengers (rear seat passengers complain that it's not cool enough, even on the highway).

I know the merits of converting back to R12 and plan on doing that eventually, but in the meantime I am interested in trying Freeze-12. I plan on having the existing R134A professionally reclaimed and would use the appropriate sticker and fittings. I would pull a vacuum before charging.

Here are my questions: Where can I get Freeze-12 in the DFW area? Is Freeze-12 compatible with the PAG oil currently in the system? Everything I read talks about compatibility with mineral oil but says nothing about PAG. I would tend to think it would be OK since Freeze-12 is actually composed of 80% R134A, but maybe someone with experience can tell me. After charging, would I just attempt to duplicate the recommended R12 system pressures? And finally, can anyone here confirm that it will get colder than R134A? I know my system was designed for R12 and that R12 will produce the best (read: coldest) results - would Freeze-12 yield results somewhere between R12 and R134A?

If the Freeze-12 isn't compatible with PAG, and I have to open the system and flush the oil anyway, then I'll just go back to R12. Either way, anything's better than the 58 degrees I'm getting right now (my 300E with original R12 system consistently gets 38 degrees - I have been measuring vent temps on all my cars for the past couple weeks).

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

a 40 degree drop or difference between ambient and vent temp is normal and anything more is asking for alot out of any a/c. measure vent temps/ambient in any central home hvac unit for an example.

all this talk about 38 degree vent temps...the fsm says 48 degree vent temps and anything lower than 41-42 they say to check the evap temp sensor for proper function so as not to freeze up or flood the evap. the ets is supposed to signal the comp when evap temp gets too low to cut off. the fsm also says at 104 ambient 68 vent temp is normal (of course humidity plays into this also). on low fan the vent temps drop cause evap has chance to build up. at high fan speeds air is moving accross faster and it is playing catch up.

the main plus with R12 is using mineral oil which is the most superior in terms of lubrication and less moisture absorption. the R12/mineral oil is/was a great combo!

the W126 has alot more cabin area to cool than a W124, is your console rear vent working? i have noticed the same as you on mine. my 1993 134a oe has 2 aux fans and a bigger/diff design condenser.

might consider a 35% light transmission or less 3M window tint job. vac/clean/comb condenser, remove blower motor and do the same for evap.

__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

Thanks for the tips. I'm with you - 40 degree difference is quite an accomplishment but then it really doesn't seem sufficient. And my other car (W124) really does blow 38 degrees, regardless of what FSM manual says. I want that in my W126! I recently tinted front and rear with 20% light transmission, and fixed the rear vent to blow A/C; both have really helped but it's still not good enough. Condensor is clean, but I have no clue about the evap. Is it hard to clean it and/or can I cause a leak by disturbing something so fragile? How do I go about doing this?

I will say that the volume of air coming out of the vents is almost nil, even at high setting. With blower on high, if I hold my hand a foot away from the vent I can just barely feel air blowing on it. In the back seat the air is definitely stagnant and hot. Could my evap need cleaning?

I'm still looking at refrigeration because the "cool" suction hose really isn't all that cold and it doesn't even sweat. I know this is not normal, and I attribute it to the R134A which the system just wasn't designed for.

Any thoughts on Freeze-12 mixing with PAG oil?

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

"the main plus with R12 is using mineral oil which is the most superior in terms of lubrication and less moisture absorption. the R12/mineral oil is/was a great combo!"--James L

That is a particularly important point for most of the people here on this forum... because most of us have the Delco Scotch Yoke four piston compressor...

WHICH DOES NOT HAVE AN OIL SUMP....
( the old York does )

So the only lubrication it gets is what is taken around the AC system by being mixable with the refrigerant...

Something a lot of refrigerants don't do as well.... so this is an important point in addition to it being the more efficient molecule with regards to cooling....

gmercoleza ,
The symptoms you describe could easily be caused by blocked fins in your evaporator... a pain to get to and clean ... but at some point the only thing to do to help the system ...

leathermang, you think 58 degrees is acceptable under the conditions I described? I agree, if the volume of air was 2 or 3 times greater, I would probably be happy.

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

The average home window unit is expected to put out air at about 6-8 degrees under the temperature which it takes in...
You don't want the actual temperature in your cabin at 58 degrees... so if your system had the ability to take your ambient air to 70 quickly for instance you would probably be happy... so the total volumn capacity is what you are needing.. which can easily be an obstructed evaporator ...

Anyone have an opinion of ester oil vs mineral? I bought mineral and planned to buy a single
application vial of UV dye, but can't find any locally.

The guys at Carlisle Auto Air suggested ester premixed with UV dye, and I found
a couple of brands localy (including Castrol) but I wanted to pulse the board before proceeding.

Opinions please?

Actually that was a quote from James L. in my post....

Those guys at Carlisle have been doing this for decades... when I try to go overboard on stuff they talk me out of buying stuff...
As a result of those types of things I pretty much trust them...
Right before I actually start to do something to my AC system I call them for the final word....

i used the castrol mineral oil form ackits.com. ester and pag do not work as well with R12 as mineral oil and certainly do not mix well. freeze 12 is mostly 134a so that is what you have now.

to clean the evap (W126), remove blower motor (clean and lube it while it is out), i then used a 1 1/4 inch hose w/ shop vac thru the opening (you can feel with hand), then blew in comp air, also used a leaf blower thru middle dash vent (open). then used ackti foam green non-acid evap cleaner/degreaser, (use hand sprayer thru blower motor or hudson type sprayer). make sure your drain works and use towels as drop cloths., let sit then spray with garden hose connected to a vinyl hose to rinse, you can also use a brush or fin comb taped to a flexable stick like on a mini blind (use string or something so as not to drop down into no mans lands). i did mine and i could feel a difference.

__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

Cool, sounds like something I should try. Where's the blower motor and is it easy to remove? Do I need to remove anything else to access the entire length of the evap? I'm guessing the hole from the blower isn't very large...

__________________
08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280

gmercoleza,
Do a search for Dmorrison's posts ( in your area no less ) ... he has done a great pictorial on getting to the evaporator... and his evap was about 50 percent blocked on the fins...
In those threads are also discussions of cleaning it without taking the whole dash out.. ( listed as about 17 hours in the flat rate manual YIKES !!)

under passenger side knee cover (remove knee cover under glove box), then the blower cover panel screws, remove blower motor screws and then remove blower motor downward, opening is about as wide as three knuckles, you will have cuts and scars on right hand! have fun!

__________________
1993 Mercedes Benz 300D 2.5 205K (ex wife's)
1984 Mercedes Benz 300SD 320K (SOLD)
2004 Mercedes Benz C240 75K
1995 GMC Sierra 2WD 5.7L 188K
1983 Mercedes Benz 300SD 239K (SOLD)
1987 BMW 325i 220K (SOLD FOR SALVAGE)

609 Certification

1984 300d Turbo 139k
Check The Voltage Output Of Alternator When A/c Blower On Max Replace Regulator Brushes On Back Of Alternator $28.50 2 Bolts 15 Min Done Diy From **************.com 13.5 Volts Plus Volts At
Battery Also Check The Front Radiator Fan Working Short The 2 Wires At The Rec Dryer And Ign Sw On **************.com Have Brush Kit For Blower Motor With Guide Book, Dieselgiant.com Have
The Freeze 12 Kit And Other Kits

I recently replaced my 1983 300SD A/C compressor . Diesel Giant's A/C page was very helpful .
The system held a vacuum a long time so I thought it had no leaks . Anyway the A/C cooling lessened over time and after about 3 weeks got to the point where the compressor won't activate . I assume that the refrigerant is gone ( Freeze 12) . At this point I think it it is time for some UV dye . Would it be okay to use that R134 / dye mix in a can from Autozone just for the leak test (I have adapters for this) ? Any other suggestions on how toi deal with this ? - Thanks