I have a 2014 Ram 3500 Limited and I had this happen at the same time my brothers '16 Charger had the same problem.
In my truck the mirror defrost button (i mistakenly thought this was my rear defrost button which my truck doesn't have) started blinking and didn't stop. While this was happening I couldn't change anything on my HVAC except fan speed. I couldn't even turn it off.
I took the truck to the dealership & the only remedy they could offer was flashing the ECM. I agreed & $115 dollars later it was still blinking. They then suggested that they could pull the whole dash & check the blend & recirc doors. I declined.
I pulled fuses, unhooked the battery - no fix. Same for my brother & his Challenger.
I finally changed the HVAC Control Module. OEM was $100 & the only tool required was a phillips screwdriver. The process took 10 minutes start to finish. I started the truck and the light started blinking but I held my breath. After the truck went through all its self checks, the light went off & all my controls worked. J did the same on his Challenger and his went back to normal as well. The light is the computer's way of telling you that self diagnosis has failed.
Apparently the module's memory can fill up and cause it to fail. Sometimes pulling the battery will cause the same thing.
Tuesday, April 27th, 2021 AT 7:27 AM