Just so the OP doesn't think I'm blowing smoke, I took the kitchen thermometer with me when I ran errands for the office this afternoon. Was 98-100 here this afternoon!

I had the temp wheel set to ~70˚ and the fan button on "Auto". When I snapped these pix, the fan was still on its highest speed.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Old school bulb style.

__________________
To see my 129 parts for sale visit:
http://stores.ebay.com/The-Mercedes-SL-Store
John Roncallo

Great information out there !! thank you

One more question, I bought expansion valve from Russia, he confirmed its old stock R12 expansion valve for W126 (I hope so)
My question is what about the 2 switches in the dryer, are they different from R134A, according to the above information, yes they are, but from where can I buy them and what are the part numbers

Update
big thanks to all who involved in this project

The result is:
Outside temp is 94F, AC blwoing 41F from the center vents on idle, engine temp is 80ish didn't move at all while idling in traffic.

The system was full of oil, the dealer charged the previous owner 4k for AC job that wasn't even blowing cold, I found 4 black crushed O rings that the dealer didn't even replace, all the switched in the dryer are 32 years old!!
replaced all pressure switches, dryer, aluminum condenser, delete the mechanical fan and replaced with electric, new expansion valve, flushed the system 4 times with acetone and dry air, vacuumed over night, R134 (no dye, no sealant)
4 doors and windows wide open, outside temp is 94F i got 40F difference so easy on idle. Thank you !!!

I'm firmly convinced that most of the dis-satisfaction with converted systems comes from a half-assed or incomplete conversion. Take the time to do it right, take the time to charge (which is an art!), and make sure that all the supporting systems work properly, and it will blow cold. Glad to hear you got it working! There are better systems out there, but for their age, they're quite good! Especially when you consider that they were designed for R12 and not R134a!

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thank you sir for everything, I took my time almost 2 months to flush, clean, reseal ... etc, charging the system was an art like you said ! a friend came in to help me he couldn't believe his eyes when I was charging with 4 doors wide open, once done door closed, boom temp. dropped to 41F.
Now I have a problem on another thread as nobody believed i got this result they thought my thermometer is in accurate or something.

38-41 is about as low as you'll ever see it go. There's a thermistor next to the evaporator coil that will kick off the compressor at 3-5˚C (37-42˚F) to keep it from growing ice. Once my SD has pulled the cabin down, it stays 42-44˚ on medium fans speeds and below.

The earlier cars will NOT work that well once converted since they had the old-school single-circuit fat-tube style condensers and woeful Delco R4 or mediocre Harrison A6 compressor. The updated '86-91 cars will though due to the upgraded condenser design and Denso compressor. The '88-91 cars got the dual-fan auxiliary fan setup (vs single 16" fan for '86-88, or single 12" for '81-85) that really helps at idle speeds and city traffic too.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I installed 80K resistor pm that sensor between the leads to lower the kicking off temp a little bit. mine was kicking off early.