Good Afternoon everyone.
I have a 2001 F-350 S/D w/7.3. Question is... Is it possible for the mode switch( one controls floor/ defrost and A/c ) to not function or should I say leave the a/c on even if it is not in a/c position? What I have noticed was that when it is in the floor mode or the vent mode ( not the floor/vent ) the compressor does not come on. When it is in vent/floor or either a/c modes it does. Is this normal... I don't think so though I do know anytime the a/c is switched on compressor should come on but no time without a/c being on.. Maybe I'm wrong

 

When is the a/c running? It is normal for a/c to run in the defrost and defrost/floor positions as well as of course the a/c positions. The a/c runs in the defrost positions as it aids in defrosting the windshield.

 

If you read the HVAC FAQs (or your owner's manual), you will find your answer....

 

The vent position is just an air flow thru function.
Should not involve the A/C.

 

You guys obviously didn't read the whole post. I said it runs in the vent/floor position as well as in the a/c modes and the defrost modes/ I know it is supposed to run in the defrost and the a/c modes. It also run in the floor/vent mode as well but it does not run in just the floor or vent modes

 

And you did not read my post.

If you had read and followed it the first time, I wouldn't feel compelled to tell you to go read it again so that you can learn how the system was designed to wok. Your owner's manual EXPLICITLY answers your question.

Link to HVAC FAQs and manuals are in my signature (below).

 

Project I stand corrected . I am sorry for the rant but I have never seen nor heard of this before. I have download the manual as this truck has none with it. Again I am sorry>

 

Okay now that you have straightened me out about the a/c portion.. My next question is.. Why would the heat come out very hot after warm up and then start blowing cold and blowing antifreeze out of the radiator cap. Could it be the water pump or thermostat. I put a new thermostat in it but it still does it and the temperature gauge never climbs above the 1/3 mark?

 

That sounds suspiciously like a blown head gasket. Do a test of the coolant for exhaust gasses.

 

Thanks project will do test and let all know results