heat only coming out of winshield vents

dodgeman1980 · Dec 2, 2016

I have a 1998 dodge ram with the 5.2 liter v8 318 engine and the heat only comes out of the winshield vents no matter if I switch the controls to different spots on the heater control please help me as the cold weather is here so I can get this fixed as soon as possible.

dudeman2009 · Dec 2, 2016

Do you get any air at all out of the other vents? Is there a hissing sound when you turn the vent selector?

dodgeman1980 · Dec 3, 2016

No I don't get and sounds at all when I switch the heater controls.

dudeman2009 · Dec 3, 2016

Then i'd start by checking the vacuum lines in the engine bay, one of them is either cracked or disconnected.

Marksman · Dec 3, 2016

I want to say that the vacuum line that feeds the controls enters the cab on the passenger side of the engine compartment around where the ac lines and heater hoses go through the firewall.

dudeman2009 · Dec 4, 2016

Marksman said:
I want to say that the vacuum line that feeds the controls enters the cab on the passenger side of the engine compartment around where the ac lines and heater hoses go through the firewall.

Yes it does, right off the intake under the airhat.

Yeret · Dec 4, 2016

I have a similar problem. My heat works fine on all settings but if I'm heavy on the throttle, the heat stops flowing until I let off the throttle again. I think that this is often referred to as "wild vents."

dudeman2009 · Dec 4, 2016

Yeret said:
I have a similar problem. My heat works fine on all settings but if I'm heavy on the throttle, the heat stops flowing until I let off the throttle again. I think that this is often referred to as "wild vents."

Your problem is due to one of two things. A bad check valve, or a really bad leak. If your vents change strong when you are light on the throttle, then i'd go with the check valve.

montrese04 · Dec 5, 2016

So what y'all are saying is there us a bad line that connects to the knob on the dash? And this line allows your blend door/vents to change settings.
Would this be why I have no gradual change between heat and cold settings? Everything works as far as vents, cool g and heating. I just don't have the option for a gradual setting. It's either hot or cold when I select

Sent from my HTC One_M8 using Tapatalk

dudeman2009 · Dec 5, 2016

montrese04 said:
So what y'all are saying is there us a bad line that connects to the knob on the dash? And this line allows your blend door/vents to change settings.
Would this be why I have no gradual change between heat and cold settings? Everything works as far as vents, cool g and heating. I just don't have the option for a gradual setting. It's either hot or cold when I select

Sent from my HTC One_M8 using Tapatalk

The blend door is either cable driven or servo driven depending on year, it is not vacuum actuated. To tell what your blend door is doing, look in the passenger footwell all the way left.

The attached picture is if you were looking in from the passenger door.

Right where the little servo attaches you should be able to see a shaft, that should rotate smoothly.

heat only coming out of winshield vents

dodgeman1980

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