Hi everyone. My brother has a 2005 hemi 2500. He's having an issue with the heater. The heater will work fine one minute, then the next it is blowing cool air. Doesn't matter what position the vents are in he says. I have a third gen diesel myself and have read that a blend door could be the issue? Then I've also read that a recirc door could be the issue? Either way, I'm on the right track?

 

are the blend doors operated with electric actuators or vacuum motors?

 

I don't know, that's why i'm here asking the experts lol

 

Search here for Heater Treater or google it. You will have to see if your doors are operating meaning the air direction when you select on the dash control, like heat defrost and floor heat. if all that is working then you will have to remove the heater motor. Very easy 3-4 bolts and its out on the passenger side. You will then have to reach up in side to see if the blend door is still in tact meaning in it position and not hanging down or broke off. Its the door to let in fresh air from outside.

All your doors are motor driven no vacuum hoses

if still ok then you might have a=
blocked heater core.
air in the radiator and hoses.
a bad thermostat

Get truck to running temperature and then
feel both in and out heater core lines bot should be about equal in heat.
check both in and out radiator hoses both should be about equal in heat.

Most of this will let you know where your problem might be.

good luck as I had a broken door for the bottom and defrost heat that was broke. I bought from heater treater and replaced the door.
I chose to not remove the complete dash and just cut out the heater box in location specified and then replaced the door and then patched in the cut housing door and works good as new done 3 years ago. So I hope its an easy fix for you because this could be a 2 day job to replace the heater core or any blend door that might be broken.

 

Sounds like it maybe low on coolant.

 

+1
no heat at idle and heat when revved and held at 2500rpm is a low coolant symptom.

 

He's not mechanically inclined at all so I'll be the one having to check things and fix things, if he doesn't want to shell out the money for a shop to do the work. I don't get to see him much so I'm trying to gather as much info as possible before the next time i see him.

I think he said it happens while driving or parked...not sure though. He just recently bought this from a dealer so I imagine that they checked fluids.