I completed a compressor/drier-receiver/expansion valve replacement by following this Diesel Giant tutorial/pictorial to a tee.

http://dieselgiant.com/repairyourac.htm

I cleaned the evaporator as best I can without removing it, and the pressures after recharging with 134a are 45psi (low side), 260 psi (high side), at 87 degrees F ambient temp, but it only blows a somewhat cool (not cold) 52 degF. Condensor is clean & in good shape.

Any suggestions?

How much refrigerant did you put into the system? My gut tells me you have overcharged it, that the high and low side pressures are too high. When using 134a you need to use no more than 80% of the amount shown for R12, and sometimes less than that.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I put approx. 2.5 lbs of 134a into the evacuated system. The R12 tag lists 2.9 lbs capacity. I also had primed the compressor and heater/drier with a total of approx. 6oz of FrigiQuiet compressor oil.

45psi/260psi at 87deg is in the ballpark of the chart I have.

Would an overcharge impair cooling significantly?

In my feeble opinion the low side is too high. Overcharging will definitely stop it cooling properly. I'd recover some of the gas and see what you get.

-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.

What part of the country are you in? Over the years I have come to the conclusion that you can't successfully convert the 123 and 126 cars over if you live in hot climates unless you change out the condenser.

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Jim

R-134a in a R-12 system typically results in significant impairment.

The car was converted to 134a by the previous owner.

The condenser should be fine if clean and all else is correct. The 85 models had an improved condenser coil that works fine with the 134. What temp are you getting at the center vent on Max/High ? and at what ambient temp ?

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

I don't know the specifics of what the high and low should be on that model, but those just sound too high. And, yes, an overcharge can impair cooling. I would double check your numbers.

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'95 E300D ("Tank") - 231,000 miles
'79 240D ("Biscuit") - 197,250 miles (Sold)
'83 240D ("Ding-Ding") - 217,000 miles (Death by deer)
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"Back off, man. I’m a scientist” ~ Peter Venkman

What prompted you to do all that work?

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My occupational hazard bein'
my occupation's just not around...
1980 300SD
1980 300SD

Have you checked those to make sure the cold air is being completed diverted to the air vents? Won't be the first time the system was working just fine, but the cold air was not coming through because the actuators weren't opening the vents to push the cold air through.

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1983 300D, the "Avocado"
1976 240D, 4-spd the "Pumpkin", SOLD to Pierre
1984 190D, 2.2L, 5-spd, my intro to MBZ diesels, crashed into in 2002

I happened to stick the thermometer in the vents of the SD today and found that it's at 54 degrees at 87 ambient.

This is also with R-134. recently recharged without evac, and it can keep the interior below 70F. at less than high blower speed, provided that the engine speed remains above 1200 rpm.

I don't believe that such performance is less than typical for the vehicle and the fluid medium that is utilized with an R4 compressor.

Those in warmer climates that suffer from 100 F. ambients need R-12 or a better condenser.............or both.

Or a better realtor.


My 240D and 300SD have both been converted to 134 "the easy way" by previous owners (meaning they didn't change the condenser or anything else that would have helped) and they're both lackluster at best. They DO cool better than "not having air at all" so I'm grateful for that, but it's far from ideal.

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~Michael S.~
Past cars:

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


Current:

1987 300SDL

Why not convert them back?

I get 52 deg F at 87 deg F ambient, which doesn't cut it for a wife & infant getting into a hot car. This about the same as what I got before I did the work.