No cab heat

[Gas Hauler]

I am having none or hardly any in cab heat. The coolant temp is in the normal operating range, yet no heat comes through the vents. A/C blows nice and cold. Any thoughts on where to begin?

Thanks

 

[DonFitzwater]

Fill out your signature so we know what you are working on. Probably a blend door... ... ... ... ... ... have you verified there is hot water entering and exiting your heater core?

 

[rscurtis]

Good advice. Make sure the cooling system is full before doing anything else.

 

[Motorhead]

Good advice. Make sure the cooling system is full before doing anything else.

X2. Low coolant will affect the heater.

 

[Spooled05]

My truck just started this year blowing cold out of the 2 drivers side vents but hot everywhere else , defrost is also hot on all 4 vents. I guess theres a door that's not functioning properly, but theres the same amount of air blowing out of the vents as anywhere else. If I put it on recirculate it will warm up on driverside .