I need some help troubleshooting my AC. Couldn't find much to relate in my searches.

Basic background:

It's still R-12. It's worked the whole time I've had it, and on long trips it would eventually freeze me out. The CCU i believe has been replaced within the last six years. Only once did I turn on the AC to have hot air blow out the vents, but after cycling the CCU off and on, it seemed to fix itself, and that was a long time ago.

Issue:

When driving, it blows "regular" air. Not hot, not cold, just air, possibly on the cool side. If I change the fan to low, I feel cold air, but not as cold as I remember it. If I turn the system off for several seconds and then back on auto, I feel cold air come out, and then the regular air feeling again as the fan speed picks up

Is maybe a flap not closing allowing outside air or even heat to mix with the AC, hence rendering it's cooling ineffective? Oh, there is also a continuous vacuum hiss sound that comes from behind the center vents when I'm messing with the AC. When it was working, I would occasionally hear a vacuum hiss come from behind the drivers side vent it seemed, but it was temporary and I figured it was just flipping flaps or something.

Please let me know what I should be looking for.

Thanks,

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1983 300SD

To me, it sounds like it's low on Freon. Has sufficient capacity to cool the evaporator with very low fan speed...........but, nothing more.

Get a set of gauges on it and see what you have. Might just need a few ounces of R-12. The compressor seals are never perfect........especially on an old vehicle.

Huh, don't know why I didn't think of that. Maybe because it was too obvious. I guess I just didn't think it would up and leak out over winter. But then again, I didn't drive it. Maybe the seals dried up...

I really need to sell this thing or drive it.

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1983 300SD

Lack of use can cause the compressor seals to dry out.

Jim

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14 E250 BlueTEC black. 45k miles
95 E320 Cabriolet Emerald green 66k miles
94 E320 Cabriolet Emerald green 152k miles
85 300TD 4 spd man, euro bumpers and lights, 15" Pentas dark blue 274k miles

Low Freon it was. My uncle has a 30# bottle of it so we dumped some in there (I had to drive to Nebraska to get it done though. Good thing I had another reason to go there.) Will see how long it holds out this time if I actually use it. Wondering if maybe I should get an oil shot and squirt it in there.

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B
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1983 300SD