Make sure that the PWM cable for the spike relay is not plugged in 1 pin off on the digital sidecar. If you don't shave off the little tab on the side of the new PWM cables, it is almost impossible to plug them in right. And even if you do shave it off, it's an easy mistake. Let's just say I'm telling you this from experience
Also, make sure you have the polarity of the power wires going into the compressor spike correct. If the LED on the DSC lights and the compressor doesn't come on, it's either a)bad DSC, 2)bad/wrongly installed PWM cable, 3) bad/miswired Spike.
Steve C.