Looking for Ideas, possessed heater

[turbo347stang]

Alright gents, I have an issue that I was hoping someone might have some insight on. In my 06 Lariat, I have the auto thermostat/control. Every once in a while it goes insane. Today, if I turn it to auto (no matter what temp I set it at) it will blow full blast out the lower vents. If I turn it to manual control it will blow out the vent I set it to, but only full blast. Then there's the kicker, if I turn it OFF, it comes out full blast from the defrost vents . Dealer said, "Yep, it sounds possessed." Not much more info other than that.

Has anyone else encountered this??

[gblauf]

I can only shed a little bit of light. Vaccuum lines under the hood and the dash control where it blows out. I have these lines come loose and it was stuck on defrost! Check your vaccuum lines.

gb

[Samsonsworld]

Right above the oil fill. Gray line. Mine's not an auto but it came loose once and caused me problems. Easy to hit when changing oil.

[turbo347stang]

Checked that one (Gray line) it is attached and tight. I did notice that the zip tie that holds it was broken, but it was still connected. The connector on the front of that black valve is supposed to be open, right?

Thanks for that.

[gblauf]

yes, should have nothing conected

[PS/Fan]

I've been doing a bunch of reading on heater problems because mine has some but not like your but I came across something somewhere about the heaters being controlled by a module.Maybe that will help you.