I have checked the connections a couple of times and they seem good.

Today the thing almost worked. The lights died down and then for a few moments the screen seemed normal with 72 degrees on both sides but still only the fan speed buttons working so I adjusted the speed down to zero and off and tried to restart the system and got only the disco light from then on.

Ordered a remanufactured controller from Mercedes. Will give that a try tomorrow. They will allow return if its not the problem.

Tried the new control unit and it worked at first, with the readout in celsius and the compressor started up, so I got out of the car and hooked up a can of coolant, got back in the car and the display started acting badly. Restarted the car and now the readout was in fahrenheit and looked good at first but would not respond and spiraled out of control to the gibberish.

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Installed the old control unit to test and the compressor kicked on and air was blowing out of the vents so I went back to the engine to add more coolant and when I go back to the cockpit the control unit was smoking and hot.
I disconnected the battery again and removed the old unit.
I need a wiring diagram and instruction on how to ohm out the harness.

I am using the service disconnect under the seat. Every time that I plug in the control unit I hand tighten the nut.
The main ground point on the firewall on the passenger side look very clean.

Where is the harmonica connector?

during the test on the unit I incorrectly had the system on with left side set to high and right side to low when they should have been set to 72F.
But the good thing is that it has no codes.
Will try to preform surgery on the original unit and will post pictures.