2012 Hino 338 cab heat issue

artice

Seasoned Expediter
Owner/Operator
Hello all. This truck has been great to me for the 10+ years I have owned it. I am stumped by the following minor problem...The truck only blows hot air in heat mode on the passenger side.. the driver's side blows cold air regardless of air flow set to defrost, dash or floorboard. The only way I have been able to get some half-decent heat in the cab is to set it to dash and close the vents on the driver's side.
At first I thought it was an actuator problem but the really strange thing is that in A/C mode it blows cold air in all vents. Any ideas?
Thanks.
 
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