No radio or front blower
 

Hello everyone,
I am having a couple problems with my 2000 DeVille DHS. I let my DHS sit for about 6 months without driving or starting it, and when I finally needed to get it going it wouldn't start. I thought it was just a dead battery so I charged it up and started it up and got a charging system message on the OBD. I needed to get it to my new house and decided it wasn't that far I'll just drive it on the battery. I turned off the radio no AC/heater or anything and just before I got to where I was going the battery died out and I had to get a jump to get it the last half mile. There it sat for a couple more months until spring where I replaced the alternator with a used one out of the same model year DHS fired it up and had no radio and no blower in the front. I replaced the battery and still nothing.

Could this be caused by the replacement alternator? I have checked fuses and power to the amp and HVAC and it's all good. I have heat and AC in the rear of the car but when it's on in the rear and I push the front defrost button the blower in the rear shuts off and when I turn the defrost off the blower in the rear works again.

As for the radio I got a IRC U1000 code class 2 data comm. malf. as well as no amp data. I checked those fuses and pulled the amp checked for power and it all checked out. The radio will turn on for 3 seconds then shut off every time I turn the key on. I suspect the HU is spent but I just don't understand why these things popped up. The only thing I have replaced is the alternator and battery. Could I have fried something by running the battery all the way down? Is it something that a dealer can reset the whole system? At my wit's end and don't want to start buying parts that I may not have to, so any help would be greatly appreciated.

Update on my situation, I replaced the amp which solved my radio problem. Still no blower in the front of car. My question is could it be the control unit that needs replaced and if so is it interchangeable like the amp was?