R134 in my 91 SDL seemes to do OK... except at idle. On hot days it will manage mid to low 40s from the vent when moving, but that goes up to like 48* at idle.

-J

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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.

I've tested my A/C out (134 with new evaporator, expansion valve, receiver/dryer) during many 98 degree days so far this summer. It has worked great. You will not be sweating, even in stop and go traffic. I don't have a thermometer but will borrow one first chance I have. I would bet I am getting 40 degrees on the freeway and 45 degrees in stop and go traffic. When I first tested it in the fall I was getting 38 degrees on low cycle (albeit at 75 F ambient). Today it was 98 F outside and I was in stop and go traffic (under shade) and had to turn the A/C to the low cycle 3 minutes into my journey. Then I remembered this post...

As I said initially, I trust that R12 might be slightly better, but if your system is in tune with a W126, R134 can be significantly better than "adequate." If you live in Houston/Miami, etc. and are in stop and go traffic for significant periods each day and want the A/C to keep you shivering, then maybe you should use R12. Otherwise, R134 works just fine.

Just my observations...

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1984 300 SD 384,000 Miles

for which vehicle are you recommending 134? both of yours SHOULD have the newer small tube condensers. most others on the forum have the large tube condensers, that are ONLY useful with 12. 134 above 84F ambient will rapidly kill a compressor on a pre84 123, on a 126, it'll be slightly better, but not much. upper 90's and 134 will likely put out a measly 60F vent temps, and the high pressures will spike above 300... unless you TOTALLY clean the evaporator, condenser, and have lower temp fan switches, and a perfectly working fan clutch.

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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!

I was reasonably impressed with the SD today. Ambient was 91F. and the SD with the R4 could manage 48 degree vent temperatures and it finally achieved the setpoint (22C) after about 20 minutes. The vent temp then dropped to about 45F. and the compressor began cycling............

The cycling results in an immediate climb in vent temps to over 60F (by feel.........the thermometer can't respond fast enough) and then the compressor engages and the cycle repeats itself.

I really need to find a better ETS.

Brian, what is an ETS please

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-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)

Evap temp switch.

It is the only device that cycles the compressor.

ahhhhh yes!! of course! I've heard you can trick them a little bit with a layer or two of scotch tape, never tried it tho

Does my '84 300D have the small-tube condenser or the large-tube condenser?

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cbjukraine
'84 300D

I believe a better trick is the addition of an inline resistor. Dave did some work on this with the W124. I need to take a look at that.

What is a good detergent for cleaning the condenser?

My newly acquired 85 300D was converted to 134a and was not cooling due to low charge (per manifold gauges). I added about 18 oz of 134a 2 days ago and was driving in total comfort in 95F ambient. I'll have to find my thermocouple DVM and take some vent temp readings.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The condenser is original as far as I know. This is on the 84 300SD.

The compressor had been changed out 8-10 years ago but I had a mechanic do it and don't know what it is. I'll take a look next time I'm in there.

A few years back I had a shop re-do the 420SEL with 134 and you are right it sucks. 60 degree vent temps is probably spot on. There must be something else wrong with it though because like I say the 300SD is awesome now with 134. It seems like it can be hit and miss with systems this old, probably more so with 134. But if the system is in good shape, 134 can be nearly as good as R12.

I wish I could figure out what is going on with the 420 SEL but my diagnostic skills are not great. I can change out parts pretty well and know some basic diagnostics but would need a mechanic to tell me what's going on with that car. And the mechanics don't really have an answer either.

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1984 300 SD 384,000 Miles

I have the same question for my 85 300D. Here's a pic of the 85, the one on my 83 looks identical.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

45 F vent temp at 85 F ambient. site glass has bubbles. Does that indicate low charge for 1334a?

I'll see how long it keeps cooling. Meanwhile I'll look for an electronic leak detector and find and fix any leaks and may try Envirosafe ES12A which I have 6 cans that I bought many years ago.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

For what it's worth, I use Envirosafe refrigerant. I've used it in all of my vehicles over many years. I just took a long drive this week with the wife down the Blue Ridge Parkway in my 240D that I installed envirosafe in years ago, and the vent temp was coming out at a chilly 37 degrees when it was 95 degrees outside. I LOVE being coooool. Envirosafe takes about 1/3 of the volume that R12 or R134 takes in the system. So far, I've had great results. But, R134 and R4 compressors do not like getting along...

R12 is always the best choice, although getting less practical.

Take care.

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D

BTW, 240D automatic with AC turned on = Causing road rage with anyone behind you when driving uphill....

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1987 300SDL #1, 1987 300SDL #2, 1980 240D, 1982 300SD, 1994 S350, 1990 350SDL, 1991 350SD, 1985 300D, 2005 E320CDI

Gone, but not forgotten: 1981 300SD, 1982 300SD, 1987 300SDL, 1983 300TD, 1980 300CD, 1981 300SD #2, 1987 300D, 1987 300TDT, 1980 300D