Hi guys, A little headache with blowing cold air on W211 E320. So sometimes it blows hot air sometimes not. Main common problem is heater valve under wipers. I expected that, but there is some non-sense about that. Let's say there is one incoming hose to it, 2 pipes to heater core, and one hose outgoing. Then normally those two pipes to heater core would be one is inlet one is outlet (I'm correct?). So lets say engine is warm in working temperature, i took out plastic under the steering wheel, and upper pipe is hot, and down pipe is cold, and interior keep blowing cold air everywhere. So as I understand that valve works, so why there is no hot air? Is there some kind valves near heater core or what? Normally if inlet pipe is hot and outlet pipe is cold, something is blocking it. And the strangest thing that lets say 4 days it works OK, and then for a week or so not working, and it starts working again when ever MB wants Any ideas what and where to check?