No heat

[jeffrosquad]

I have a 2012 3500 6.7l. I have no heat in the cab. Well, correction, blows heat for about a second then goes cold. I have replaced the water pump (it went out), the thermostat, the blend door actuator. I can see the blend door moving. I also got a coolant flush done. Only thing I haven't replaced is the control module itself (knobs). I ordered one online but had wrong connectors. Anyone else experience this or any clues as to what the issue may be? Possible that from the water pump going out there may be some piece of fin blocking the heater core? I would think that would have been fixed with the flush.

 

[Grams]

I haven’t experienced it…but you’ll likely get advice to forcefully flush the heater-core itself. THere have been reports of them being blocked by debris and “casting sand” from the engine mfr. (although, that seems unlikely to me seeing your truck is a 2012 model….as you’d likely have already experienced a problem by now.)
A “back-flush” of the heater-core would not hurt anything however.
You can probably do this at the firewall without loosing a lot of coolant by disconnecting the heater hoses and plugging the open ends of the hoses while you backflush the core.

 

[jawzs2]

I have a 2012 3500 6.7l. I have no heat in the cab. Well, correction, blows heat for about a second then goes cold. I have replaced the water pump (it went out), the thermostat, the blend door actuator. I can see the blend door moving. I also got a coolant flush done. Only thing I haven't replaced is the control module itself (knobs). I ordered one online but had wrong connectors. Anyone else experience this or any clues as to what the issue may be? Possible that from the water pump going out there may be some piece of fin blocking the heater core? I would think that would have been fixed with the flush.

99.9% odds it's the heater core. There's probably well over 100 threads on here regarding it. It's not too bad of a job, just time consuming.

 

[Daw14]

I agree the core is probably restricted, flush it in both directions until the water flows clear .

 

[mtofell]

I just went through this and agree you should flush your heater core. Here's a thread I started that explains how I did it. Post #6 is the heart of it.

Low Coolant = Low Cabin Heat?

So, my coolant level was down 2-3 quarts due to the radiator drain valve rattling loose/slightly open (at least I hope that's it - but another topic). I initially noticed the heat output being bad - lukewarm at best, then, the same day, noticed a small puddle of coolant under the front/driver...

www.ramforum.com

 

[jeffrosquad]

Thank you for the replies, I did a flush by duct taping a turkey baster tube to the end of the hose heat now works somewhat. I think I need to do another flush or chemical flush. Are the flush guns they sell any good? Or just water and CLR?