Hi Timbuk, I beleive there are 2 different models of CDC2, one which works with the CCRT700, and one that works with all other head units, ie: CCR600/800, and it appears that they are not compatible.
They are differentiated by the last two letters on the model designation, but can't remember what they are
(might be worth checking all three units you have for different lettering?)
Dave DND will probably be along shortly to explain.
(I only know because I bought a CCR600, and needed a CDC2 to match, and someone told me)
Dodger.
Yup, thanks for that, have stated they are not compatible, just proving there is power to the rear of the car. I actually have 3 here all with different part numbers. CCR600 ones power up, CCRT700 is the one that is dead