Anyone have any idea why my heat in the cabin only works when my truck is in motion at certain RPM I have a 2016 F150. I'm not getting any heat when the truck is at idle. I checked my coolant reservoir when my truck was off for the night and it is right below the minimum line but when the engine is running its between the Min and Max line.

 

Coolant must be between Min and Max marks when the engine is cold. Your coolant is low. Top it up.

 

.....and probably best not to use tap water if you plan to add only water.

 

Are you running the upgraded yellow coolant in your truck?

 

if you get bored can you upload a picture of where coolant tank sits in regard to min and max after being off all night?

 

I do worry about it being my heater core gummed up as a possible issue.

 

edit:
misinformation..... deleted

 

This is where my level sits after being off for 3 hours in below zero temps does that look low?