Suddenly lost heat in cab, 2001, 379, any suggestions on what happened?

Howdy All,

The blower fan in the cab works just fine, blows cold air when using the AC, when I try to get defrost or heat the fan works in all positions and blows air but its cold. I don't have any coolant leaks, everything electrical seems to be working so I am mystified by what happened, one minute it was blowing hot-warm air the next just cold air. The sleeper gets, warm-hot air blowing so I am ASSUMING it has something to do with the heat controls whatever and wherever they are for the cab. Any information or suggestions on how to fix this will be greatly appreciated, THANKS.

Dave

 

check the hose going to and from heater core. If the supply and return are warm, I would replace the hvac cab controls. You didnt specify whether or not you have a valve to shut off heat going to your heater control. Some trucks have them and some dont. My 379 does not. No need for a valve. My a/c is frigid. Anyhow, if the hoses are cold then obviously your valve is shut

 

Howdy Cam Roberts,

My coolant lines do have valves in them, the valves are in the the OPEN position as they always have been since I have owned the truck about a year and half. I have not felt the lines going into the cab heater core but have verified that the valves are open. As I do have heat in the sleeper, I am ASSUMING something is wrong going to the cab. I have watched a bunch of youtube videos looking for something that might give me a clue but have found nothing that pertains to my situation. Thanks for your post and suggestion.

Dave

 

no problem i wish i could be more help. My truck is a day cab.

 

My WAG = Low coolant?

 

Howdy FozzyNOK,

Nope, that was the first thing I checked, its right where it should be. Coolant and engine oil temperatures are right where they should be so its not a lack of coolant.

Dave

 

It was a guess.. lol.. My daughter brought her car home saying that she had no heat... I checked the car... I helps to have SOME coolant to get to the heater core! lol

 

Most likely a failure in the control of the temp blender. Not sure if its cable or electric actuated on your truck or not Dave but @pushbroom will know for sure.

 

Howdy Roberts450,

@pushbroom, has helped me out before, perhaps he can chime in and enlighten myself and others who may have or someday will have this problem. Thanks for your post.

Dave

 

Blend door actuator (motor)