No Heat

   / No Heat #1  

fruitcakesa

Veteran Member
Joined
Mar 10, 2015
Messages
1,142
Location
CavendishVT
Tractor
M6040 JD 450C
So I had the opposite of this issue a couple years back where I would get heat all the time when I tried running the AC or even just the fan.
I was told I had a failed heater valve and instead of finding and fixing it, I put a ball valve in one of the heater lines and used that to turn of the heat and was able to again get cold air.
Now, 2 years later, I get no heat. Yes I opened the ball valve to allow heat flow but all I get is cold air output and my temp gauge shows engine temp up to normal.
Where do I start looking? Could this be a problem with the climate control or temp switch or something in the heater itself?
 
   / No Heat #2  
Could be the original valve, I assume it is electrically activated, or circuit has closed.

If we know what it is you’re working with, we can armchair diagnose for you
 
   / No Heat #3  
Typically the cabin temperature is regulated by temp blend door moving to allow warm or cold air to be distributed to vents. Usually in automotive or ag equipment the water flows through the heater core regardless of whether hot or cold air is being called for in cabin. The blend door directs airflow over AC evaporator or heater core based on setting of HVAC temp control. Fault could be in temp control head not telling blend door to move or in the blend door actuator not moving blend door. Guessing door is stuck full cold right now not allowing airflow over heater core.
 
   / No Heat #4  
Or the heater core is plugged and needs back flush or R&R.
 
   / No Heat
  • Thread Starter
#6  
The heater is located under the seat so access is somewhat ok. I need to get a breakdown of the system to locate the potential problem areas.
 
   / No Heat #7  
Plugged heater core is possible due to water supply being turned off by the valve that was installed. Would not explain warm air when controls were asking for cooling last summer. Best test for heater core flow is measuring supply and return temp of heater core hoses. My money is on blend door problem based on the description.
 
   / No Heat
  • Thread Starter
#8  
Are the blend doors electrically controlled by the climate switches?
 
   / No Heat #9  
The three common methods of HVAC control are cable (very old vehicles) vacuum (with a vacuum pump for diesels) or electric solenoid (most modern vehicles)
 
 
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