No heat ... blend door?

Hello -

I'm new to the Prius world. I picked up a 2013 wagon last month (157k), very clean, but it was unseasonably warm that week. Soon find out there's no heat. All the controls work except it blasts cool air.

I took it to a shop for a diagnosis. There's nothing wrong according to any of the computers. The coolant is a little "dirty" but the mechanic doesn't think that's the problem because it seems to be flowing. It's hot going into the core, and hot coming out. So, by process of elimination, the mechanic thinks the problem is likely to be the blend door actuator.

Based on his explanation and what I could understand on the Internet (I don't have a mechanical background), it would make sense. BUT it's a $1000 job because he has to lift the dashboard. And he doesn't know for sure that's the problem.

Any other ideas of what this could be? I would really hate to drop $1000 and find out it's going to be, oh, you have to replace the whole HVAC system.

Thanks in advance for your advice. I bought the Prius because it seems to have a reputation for low maintenance costs compared to other high mileage cars, and I thought I had a sense of the things I'd be taking a chance on (the battery, the head gasket), but heating wasn't on my radar...

 

Update, for posterity:

I took it to a second mechanic (both are well rated hybrid specialists - I wasn't able to get in to see dealer) who was able to see the blend door was operational. However he noticed the coolant was the wrong color. He flushed and saw white gunk come out. Apparently someone used some kind of head gasket sealant shortly before I bought the car. I had to replace the leaking head gasket plus the radiator, which was fouled up from the sealant. The mechanic hosed a special cleaner through the system to clean out the core (fingers crossed).

A week later the heat goes out again and I get a high temp warning on the highway. Coolant reservoir is super low. Take it back - the engine water pump is dead.

Total is $3700, more than half what I paid. Talk about a money pit. Of course if I had wanted to spend over 10 grand I would have gotten a lower mileage car!

Mechanic says the sealant should only affect the head gasket, the radiator, and water pump, and the core, so I should be in the clear from this God forsaken mess. Does that sound right?