84 300D Automatic Climate Control problems

Well, I have read every article I can find on how to diagnose and fix the automatic climate control (ACC) on these early 80's W123's, but my symptoms do not seem to be typical. So, I was wondering if anyone
could enlighten me, or direct my investigations further. Here's the problem. Its long, so bear with me, I tried to be specific.
When the ACC is on 'Min' temperature, it works fine (economy and the others work as directed). When it is set to any other temp (e.g. not on Min), it blows out HOT air only. This is not the condition where the fuse for the A/C burns out and blows out only hot air (I've had this also, but fixed it). Additionally, the A/C leaks freon, so its not always full of freon. Its been converted to R134a, but I think its an old conversion (the high pressure fitting is a strange size). I recharged it pretty regularly during the summer, but once fall got here I just started letting the windows down. Now I have to let the windows down to get all the HOT air out of my car.
Things I have tried so far: Checked the temperature sensor tube running from dash to blower box. Its a good quality rubber hose that's been replaced recently, so no apparent problem there. Removed and inspected the monovalve under the hood. It seemed to be stuck and had some gunk on it, but otherwise seemed to work. I cleaned it and checked the operation by hand. It moves and rotates, so if that's wrong, let me know. The copper screen looked kinda "smushed" but appeared intact. (This things only about $40, so I can replace it if necessary) I thought cleaning this would fix everything, but it didn't. I have checked for proper operation of the main air flaps behind the glove box. All seem to work properly (according to service manual specs), except for when I switch from off ('e') to economy ('d'), it doesn't open the flaps correctly.
The only things I can think of that it could be is a broken solder joint in the unit (seems to be the most common problem), or the A/C provides more temperature control than I thought, and needs to be charged for it to work correctly. I don't think its the latter though, because it did this during the summer when I had a full charge of freon, and would turn it off 'Min'. Also, the compressor doesn't run on economy mode (according to the service manual), so it should temper the air correctly even if there is no freon on that setting.
Any thoughts or comments are appreciated, if I left anything out, or did something wrong let me know.
--Doug
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Bad mono valve insert. Replace it.

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System defaults to full heat when mono valve fails.
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On Jan 17, 8:25 pm, "-->> T.G. Lambach <<--" <"T.G. Lambach at NoHamorSpamcomcast.net"> wrote:

Thanks guys. Appreciate the quick replies.
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