Yesterday my 2004 climate screen popped up to check the AC connections. I searched around and saw the solution was to put in a new mfd. I took the car to toyota and the worked on the car and came to the same solution. I replaced the unit twice with used displays from wreckers. Same problem. I paid toyota more at this point and the decided the AC ecu was bad and replaced it. Still didnt fix the problem and we tested it with both replacement mfds and the original. Toyota is back at it trying to find the problem. If the steering controls worked, I would just leave it as it is, but they havnt worked in over a year and 100k miles. They have no clue whats wrong. I cant drive customers around with no heat. Does anyone have any pointers or areas I should tell them to look at?
Maybe your coolant needs to be replaced? There have been several people that have loss heat in their cars due to air in the coolant loop. Make sure there is no leak in your water pump. If your coolant is low, try topping off the coolant and get all the air out of the system.
OP, changing the clockspring might get the steering column controls working again. Check the coolant level at the radiator, not the overflow. If it is low, the heat won't work well even if the fan controls and or the MFD was working. If you can't figure it out, go to Luscious Garage. They can do wonders with a Prius. Best of luck to you.