Rear bunk fan switch blinking

When that light blinks it means low voltage, check your batteries one or more could be bad

 

that rear panel is the most sensitive voltage point on a volvo it will start beeping and blinking when it sees low voltage, 04-06 had connections in the back that would corrode and drivers would go crazy cuz it would never stop beeping no matter what until the problem was fixed. It's a real piece of work as far as modules go i've had it cause a bunch of problems. Once i had a driver swear his truck was possessed when he was sleeping the sleeper light would come on and then blower and it would shut off in a few minutes all was being caused by a loose ground contact in the back of the module.