C280 Heating/AC problem

[DDZ]

I have read quite a bit about my problem here already and still have a couple of questions because I can't find anything definitive for my vehicle. I have a couple of problems with the heating and AC on my car. The first is that, like a lot of others, I have warm air constantly out the side vents. The other problem is what comes out the center and defrost vents. I am thinking I may have more than 1 failure also.
I have checked in diagnostic mode and seem to have proper sensor operation for all sensors. The in car temp sensor goes up/down, the outside temp sensor seems correct, the heater core temp sensor hovers around 140 while driving, the evap temp sensor hovers around 38F. My first time pulling the PBU errors I had 12 different codes which I cleared. The one that does come back is 52 which I haven't been able to determine through searching this site what it means. Also, I can switch vents with the pushbuttons and they all switch correctly.
So, I have warm air out the side vents constantly. Most times the center vent will switch between warm/cool for the first 10-15 minutes and then will only put out warm air. Sometimes it will only put out warm and never cool. The outside temp here is around 45 today.
Now for the questions. I traced the heater water line from the engine. It first goes to a device under the air intake filter that could be a pump or a valve. Then the piping out of this device goes to another device in the area by the firewall, passenger side in engine compartment under that large plastic cover. This device has 2 hoses coming out to the firewall. It has a 3 wire connector and 2 cans on top. My initial questions are these. Is the first device a pump or a valve? Is the device by the firewall a duovalve? What do the 2 hoses feed? Could this device being stuck open on 1 of the 2 cans be causing the constant heat from the side vents? I assume this device is controlled by the CCU. Does the CCU send out a signal to each actuator individually and if so when. If I knew the answer to this question I could put a voltmeter on the connector to see if the CCU is doing it's job.
I am guessing that my CCU may be flakey. I think it is failing when heated up. Before I spring the cash to get a replacement one from my local junkyard I would like to check some of it's outputs to verify. One other note on the CCU. Recently it doesn't remember the state of the pushbuttons when the car was turned off.
Thanks in advance to all replies....