No, there aren't typical causes on the w126.
Um, yes, there are some typical causes:
You said your condenser was replaced recently, can we assume a correct and full charge? And is it R12 or 134?
One 'Typical' problem after freon is the compressor, is it kicking on? Can you see the clutch engage? When it does kick in, if it kicks in, then do you see bubbles in the sight glass? (By the left hand headlight) See if it is bubbling, if it is, then you should be good on freon and the comp should be working.
The next 'Typical' AC problem is the vacuum pods which control the air direction flaps. What happens over time is that the rubber diaphragms in the pods that actuate the flaps deteriorates and cracks and loses the vacuum seal. When this happens the AC system goes to 'default' position which sends all air to the defrost vents to keep it clear. I wrote a whole thread on it with a DIY if you care to read it, search for my name and 'Finally Fixed' in the threads I've authored, If the pics are missing, and you want the service manuals as well, PM me your email and get your reading done and up to speed, and then I will help you with any additional questions you may have.
Another 'Typical' problem is the expansion valve. It goes, and the receiver/Dryer bottle should be replaced by now. The Exp Valve is a bitch to get to. I had my entire dash and the Bendix AC box out when I did mine, and it was easy then, but it's a bitch to get to with everything in place. Not that it's hard to get to per se, but the connections are a bitch to make without possible stripping of the threads for the pipes.
There is not any function of the A/C & Heating system I do not understand, nor can help you fix. It's an easy system to troubleshoot, but greasy and messy to fix, that's why tey charge so much at the Mechs. But if you have the aptitude and time, I can and will guide you through it.
I will also send you the complete manual sets digitally and a lot of other docs I've collected over the years. Look through my threads and you wll see many DIY's I've done. It speaks for itself.