Heat then no heat

[bigbrat]

2017 1500
I have heat coming from my vents..I switch to defrost and loose my heat.
I go back to vents again and have no heat there ..what could be wrong

 

[mtofell]

If you're getting good hot air in places and not in others it's likely a blend door issue. If it just starts out hot then goes cold everywhere it's likely a clogged heater core (common issue with these trucks and a somewhat easy fix most times if you have some basic tools and skills).

 

[Burla]

Ground zero for casting sand issues 2016 the most cases 2017 as well, either clog or blend door issue. You can try rmi-25 might or might not help, also flush heater core. Blend doors labor is $$, but you need to get on this winter is here.

 

[bigbrat]

Ground zero for casting sand issues 2016 the most cases 2017 as well, either clog or blend door issue. You can try rmi-25 might or might not help, also flush heater core. Blend doors labor is $$, but you need to get on this winter is here.

Ive put a bottle of RMI-25 in already

 

[SitKneelBend]

Ive put a bottle of RMI-25 in already

Did you backflush the heater core?

 

[bigbrat]

Did you backflush the heater core?

Yes

 

[SitKneelBend]

Yes

This is what came out of mine...

3.6L Radiator Fan Problem?

Way above my pay grade lol Anything is possible and I just don’t have any background information other than the Dorman unit was well built with a smooth mating surface that included all seals and accepted the new OEM sensors without issue. Overall I’m pleased with it coming up on six months...

www.ramforum.com