03 XL Rear A/C not working

Hi, Have an '03 Envoy XL 2.8L 6L with dual climate control and rear A/C as well. My front a/c lost speeds 1-3 but 4 & 5 worked. After research I learned that it was the blower resistor. Original failed resistor part number was 15415789 RBE 1 REV 001. Purchased replacement AC Delco part number D15 15-80860. Installed and all my speeds on the front A/C work but my rear a/c didn't. Asked the company I purchased it from to verify the AC Delco part was the correct one for my vehicle. They checked and said it was and sent me another assuming the first was defective. Installed the replacement and once again all speeds worked in front, but no a/c in rear. I have a rotary switch in front by the gear shift that has 1-2-3-RR to control the rear a/c or the RR setting shifts control to the rear panel which has a speed switch, temp switch and air flow switch. Tried every combo with no effect. The original and replacement resistors look different, but didn't think that too unusual. Now I don't know if it is the wrong resistor for my vehicle or if the rear A/C was damaged when the resistor went out. Is there only one blower or do I need to look for another. Any idea where I should look next? Thanks in advance for any help......