My 2010 Ford Explorer only blows out hot air even if I have the AC on. Everything seem to work on/off and the different speed settings. There is no clicking, or no other abnormal sounds. Could this be the blend door actuator? Thanks,

I assume you are talking about mercedes c300. Is that happening when you set on auto. What happens when you set temperature to lowest settings? When it blows hot, is it hot or warm? Does ac compressor works when you blow hot air? There could be few possibilities: low freon, faulty temperature sensor in the cabin, faulty ac controller, sticky ac/heater door or faulty door motor

Two possibilities. One is the blend door actuator is bad ( located under the dash, in the center). Or the controller is bad.

If both heater hoses are hot, and the radiator is full of coolant, it may be a blend door problem under the dash.
The blend doors direct air thru the heater core and out thru the vents.
It may still be under Ford warranty.

charge the a/c add a/c dye and ck. for leaks

There is a Flap on heater box and on some of those it is motor controlled, but it sounds like the flap is not switching back and forth

your problem is in the blower motor speed controller and it is near blower motor

First you need to make sure your testing you ac when the car is on. If its still blowing hot air make sure you have the ac setting set and not the fan setting. If thats not the problem make sure the compressor in the ac is running it give off this distinct humming sound when the ac is turned on, you might need to put your ear next to it if you can find it. If the compressor isn't working check the wiring in the car, and make sure the fuse/chip for the compressor are fine.

where does the air blow out at? ie floor, vent , defrost. do you hear any unusual noise when changing from hot to cold? ie a clicking noise

Sounds like your temperature actuator is not moving or your temp door is broken. On max a-c ,coolant is shut off to your heater core allowing only cold air in.

change your Heater Control Valve. I've seen a quite a few of them do this and it's almost always the valve