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Hot air from vents with AC off / 2021 3500

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Running down the highway, 60+mph, a/c off, fan on high. I get hot air from the vents, as if the heater core is active. The temperature knob is set all the way to blue, still hot.

Is there an inline solenoid that stops coolant flow to the heater core when heat is not wanted?

If not, can I add a valve to the heater core feed to stop flow? Dont want to run the ac all the time, it smells on startup/restart. Should be able to get outdoor air temp thru the vents. I valved off the heater core in my 01 jeep cherokee with good results.. the ram tho, not sure

I`m thinkin theres some circ issue or coolant air vent issue that would prevent me from valving the heater core off.. Lookin for some advice from someone experienced in this.

thanks!
 
That's normal, it's the heat from the engine bay and the heat that is inside the dashboard and so on.
Without AC you hardly ever see numbers below 90 at the vents.

If yours is smell, do you have a fresh air filter installed, if yes changed it at least annually?
If not, install one after a cleaning of the AC coil.
There should be no small from the AC.
 
I have to disagree, I get whatever outside air to come in, it's not HOT. I just set trap to what I want. NO I don't use AUTO.

Maybe I am not understanding the question.
 
The heater core gets full flow all the time. There are blend doors that bypass the airflow over the heater core based on the temp setting.

What’s the ambient temp when this is occurring?

I have to disagree, I get whatever outside air to come in, it's not HOT. I just set trap to what I want. NO I don't use AUTO.

Maybe I am not understanding the question.

My trucks have all worked similar to what Ozy described. I need AC engaged anytime is above ~50° outside to keep the air cool, but I also run AUTO nearly all the time.

A Jetta wagon I had several years ago would need the AC working anytime it was above 40° outside because of all the glass. When I got the windows tinted I was able to use the AC a little less on cool days as long as it wasn’t sunny and clear.
 
My dealer service didn’t have cabin filters when I ask a while back. Going to make a Genos order soon. What do I need for my 2022 it’s a bit confusing
 
Just think in 23 years I never changed the cabin filter. I’m bad

Your old one didn't came with one, which was bad as it was already state of the art in mid nineties to have a cabin air filter.
So nothing wrong from your side, there was nothing to change aside from a plugged AC coil after a couple years. Moldy and Stinky, rotted away in road side debris.

On my 04 I was shocked to find out it came without one, not even have a provision to install one.:eek:
That was just bad engineering, cheaped out at the most important part for travel quality.
 
That's normal, it's the heat from the engine bay and the heat that is inside the dashboard and so on.
Without AC you hardly ever see numbers below 90 at the vents.

If yours is smell, do you have a fresh air filter installed, if yes changed it at least annually?
If not, install one after a cleaning of the AC coil.
There should be no small from the AC.

Not a huge smell when I turn on the AC, its more of an issue that I use my truck for work, and I`m in and out of it alot. Going back and forth from ac to not ac makes yer body confused, and ya sweat like a pig. No bueno.

Ambient temp while on highway at 60mph is like 80F max so far this year.. Air coming out from the vents is at least 10-15F higher than room temp. I can accept it producing hot air while sitting in traffic, but not at speed. Which is why I think the core is hot, and maybe the blend door doesnt stop it? hm. The ac does work well when I call for it tho

I do have max care, but dread going to the dealer. The hvac system has worked like this from day1, my old 16 was the same, but wasnt quite as bad
 
If it’s 80°F and you’re only getting air 10-15° higher than ambient you do not have any issues.

Use your AC and set the dial to the temp you want to be accustomed to.

I find my body to be the opposite, short bursts of AC makes me sweat much less since my core temp drops a little with the AC so it’s able to stop sweating.
 
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I'm thinking its either normal (I absolutely use AC if it's 80º outside) or maybe an issue with the electric heater (if the '21's have them).
 
Shouldn't be a difference on a new vehicle.. but anyways, how much difference with the AC off?

I think it absolutely will. Even if the vents and blend doors work perfectly the hot heater core is still contaminating the HVAC box. Remember, my immediate complaint of the AC performance on my '21?

There is a long history of AC complaints on Dodge/Ram since 1994, when the switch was made to a full flow heater core. Prior to '94, Dodge used the vacuum shut off valve, those trucks will freeze you out.

When Dodge switched from 180 degree t-stats in '99 to the 190, the complaints seemed to get worse, then the 200 was even more so.

I do recommend that if you do shut the flow off to the heater core that you use two valves and just bypass it. I think the bypass flow is important with the higher revving late model Cummins engines.
 
I do recommend that if you do shut the flow off to the heater core that you use two valves and just bypass it. I think the bypass flow is important with the higher revving late model Cummins engines.

I completely agree, the coolant flowing thru the core is important.

You could do it with a single Y valve and T on the return line too.
 
I think it absolutely will. Even if the vents and blend doors work perfectly the hot heater core is still contaminating the HVAC box. Remember, my immediate complaint of the AC performance on my '21?

There is a long history of AC complaints on Dodge/Ram since 1994, when the switch was made to a full flow heater core. Prior to '94, Dodge used the vacuum shut off valve, those trucks will freeze you out.

When Dodge switched from 180 degree t-stats in '99 to the 190, the complaints seemed to get worse, then the 200 was even more so.

I do recommend that if you do shut the flow off to the heater core that you use two valves and just bypass it. I think the bypass flow is important with the higher revving late model Cummins engines.

I completely agree, the coolant flowing thru the core is important.

You could do it with a single Y valve and T on the return line too.


For now I run the single shutoff on the standpipe coming off the head. There’s a mega thread on another forum about doing it this way with no ill effects posted as of yet. Real estate is tight in there and doing the bypass method would be a bit tricky.
 
For now I run the single shutoff on the standpipe coming off the head. There’s a mega thread on another forum about doing it this way with no ill effects posted as of yet. Real estate is tight in there and doing the bypass method would be a bit tricky.

That will put increased coolant pressure at the rear of the block under high load and rpm.

It may not ever pose an issue, but these motors are known to run high pressure in the block.
 
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