I have a PF condenser and sanden on my 1984 and factory compressor and condenser on my 1982. To be honest, I don't notice any difference at all in vent temps at highway speeds between the two cars. The sanden/pf system does better in stop and go and idle functions. If you are only seeing 50 vent temps on the highway, I would look deeper at what is not right in your current system before upgrading.
I am assuming those 50 degree readings are with the fan on low after 10 or 15 minutes on the highway. If so, then something else is wrong. If 50 is what you are seeing on high fan with triple digits outside, then that is all you can expect from the system and the pf condenser won't help.
Fundamentally these systems needed a bigger evaporator to really cool the cabin in high temps. The Germans didnt have those high temps and didnt design the system for them.

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1985 300 TD 448K
1984 300 TD 278K

1983 240D euro 240k
1994 f-250 idi turbo 330K
1986 f-350 IDI
1987 F-350 IDI

1985 JD 1050 4wd
1965 IH 3660

Carl -figured out the hose situation then came back and saw your edit. Thanks for that one.

Shadetree- I’ve been wondering about the bottleneck in these systems. Did not suspect the evaporator… also, great to have a range of reasonable expectations regarding performance.

Stellar opportunity to system test at the moment, being out in the desert.
It was about 97 yesterday driving through Joshua tree and I was getting about 43 at the vents(this is on fan setting 2). Condenser wasn’t my issue in the end, it was the aux fan. Again. One of the brushes was getting jammed each time the armature spun down. The first time I addressed it, I didn’t remove enough carbon from the base and a week later found it jammed again. Now that the fan is working as intended, I’m pretty satisfied. I’ve got a few extra cans of duracool. Going to wade deeper into the summer before doing anything else.

For now, I think I’m done

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1981 240D 4sp manual. Ivory White.

That’s really great news. 43 is extremely cold for 97 ambient.

Just in time for summer. There’ll be a lot of opportunities to test it out.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

It being Joshua Tree, I'm a little skeptical of the outside temp... likely cooler. Still very satisfied. In the future, I may consider doing the w126 fan upgrade should I find one at the JY in reasonable condition.

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1981 240D 4sp manual. Ivory White.

? The cooling fan or the condenser fan ? .

I removed the finger guard / debris screen and my 240D's auxiliary fan is *much* quieter and cools better to boot .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Condenser fan.

The post 86 w126 fan is a bit larger… 16” from memory (don’t quote me)

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1981 240D 4sp manual. Ivory White.

Thank you Shern ;

I'll have to give that a look .

New ones are not too $pendy, at this late date any used one will have worn / dry bushings and brushes too .

Plenty of aftermarket electric fans available too .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

The replacement condenser temperature sensor finally arrived at the dealership.
I was concerned it’d been sitting on a shelf for 20 years but the mfg date was stamped on the label. August 2019.

I get the thing home and break out the multimeter. Guess what it reads… 18.5k.
This was the original reading of my pre-modded sensor. Another thing: no resistor.
Looks like this one was not trimmed from the factory or otherwise.

Now based on my reading, I have no reason to suspect performance any different to the original. And yet… I’m curious. If it does work, it’s for reasons that are beyond my knowledge.
If it doesn’t, I’m wondering if the issue wasn’t in the AC wheel’s potentiometer. As expected,
with probes connected to each prong of the wheel you can watch the resistance rise and fall with each position change of the wheel. Again, without a baseline it’s hard to know for sure.
At the moment, we’ve only three data points. My original (18.5k), H3ffe’s original (14k) and a NOS replacement sensor (18.5k).

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1981 240D 4sp manual. Ivory White.

I realize that I do not understand the differences between what I referred to in the initial post as "alt refrigerants." Is envirosafe considered 12a? Which are considered CFC blends to be avoided?
mobdro app

R-12 is Freon. It is what most of these older cars were designed to run. It was banned, so in the early 90s they swapped to R-134a. R-12 systems can be retrofit with mixed results.

12a is a hydrocarbon blend. Propane and butane. The temperature/pressure behaviors are similar to R-12. The issue is that in a leaky system, the more volatile component will leak first, which results in a changing temperature and pressure characteristic. Folks also don’t like the idea of a flammable hydrocarbon in the AC system, though propane as a refrigerant is used industrially.

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

Your response is great, but the guy you’ve replied to is also a spammer/scammer.
His post is a copy paste from my initial post.

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1981 240D 4sp manual. Ivory White.

Ugh… rrrrrrr….

Thought spam posts had embedded links. I don’t get what these people are doing… trying to establish an account so they can pm and scam people in the classifieds?

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Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

Could be a number of spots in the thumbwheel circuit that have drifted out of spec.

Did you measure the sensor resistance at the same ambient temperature? It was a pretty cool day today which may result in a slightly higher resistance if you didn’t replicate temperatures.

I’m not too sure what is going on here. Perhaps the MB part has drifted? Unlikely given its age and it hasn’t had any electricity run through it.

Whatever you do don’t touch your car unless you want to do this all over again.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

Don't over think things, it's very easy to do .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

More curious than anything else.

I went to the JY today and pulled another Evap sensor and thumb wheel from another 81 240d. Another 18.5k on the sensor (factory trimmed like my original), and similar thumb wheel readings to what I have (approx 55.4 max setting, 40 one notch before min). Spoke to H3ffe who shared similar readings on his two thumb wheels. If nothing else, I’m quite happy to have a few additional data points. Makes grasping in the dark a little less onerous. This will likely come in handy for someone down the line.

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1981 240D 4sp manual. Ivory White.