Heater not working properly

Hi,

Do you get heat at the floor? The interesting thing is this. There is a heater control valve that will determine the amount of heat you get. If you have heat at the center vents, then it's working. Next is a mode actuator which is what changes the air flow direction. It sounds like that too is working. The problem is there is only one heater core so if direction is changing but you lose heat, something must be happening with the mode actuator linkage. Tell me, are any of the lights on the control panel flashing? See pic 1

The only other thing I can think of is if the mode door is somehow closing the blend air door when it moves. Do me a favor. Locate the air mix door cable under the dash. Interestingly, this vehicle has a heater control valve under the hood to allow heat to enter the vehicle, and then a blend air door cable under the dash to adjust heat. One actuates the other. I attached a pic (Pic 2) that shows what I am referring to. The air mix lever is letter C. Turn the heater on so you have heat from the vents. Then, while you are watching the air mix lever as seen in the pic, change the air flow direction and see if something is moving that lever or causing it to move.

Do that and let me know what you find. Sorry this is so confusing. I just sat here for 30 minutes trying to figure it out for you, and this is the best I can think of. It really doesn't make sense because two things are changing when one is called for. To make it more confusing, heat in the heater core doesn't just go away in a second. Something has to be causing it to bypass and blow cold air. Something must be changing the air mix door to cold.

Let me know.

Joe

Hi,

That is what I am suspecting. In pic 2, that is the temp door actuator. The cable in the picture runs to a heater control valve under the hood. When the heater control valve is opened, coolant flows through the heater core. The other lever is for the blend air door (aka air mix door). Based on how far open or closed that door is determines how much heat you get. Try to locate it. If I recall (and this is from memory) it is located center facing the left side of the vehicle (driver's side). It's a stretch, but I am thinking something is allowing that actuator to move when you change air flow direction. If the heater control valve was the problem, you wouldn't have any heat or you wouldn't be able to turn the heat off. Plus, once the heater core is hot, it doesn't just instantly cool off between switching air flow direction, so you should still have heat for a short time. The only thing I can think of that would shut heat off instantly would be the blend air door. (Aka air mix door).

Let me know if you can locate it. If you do, see if it moves when you change air flow direction. Or, turn the air flow to defrost and move the lever manually to see if heat starts coming from the defrost.

Let me know.

Joe