Heating and cooling ducts

[NotSteve]

Does anyone know how the ducts work behind and under the dash. When I put my controls into defrost only or floor only, air still comes out other vents. I'm assuming as the truck gets older things don't work as they should.

Has anyone fooled around with this? I assume the ducts work on air pressure. Is there a pressure tank or valve that may be weak and needs to be replaced? Should I oil the axles on the vent doors? Is there a foam pad around the vents that needs to be replaced?

As an example. When I turn the AC and fan on full blast it really doesn't come out the face vents very good. When I replaced the blower motor I turned it on before putting the cover back on and it was like a wind tunnel but it's not the same coming out the vents.

[pdm]

Check the hvac filter, if it hasnt been lately. It can affect the volume of air. I think its on the passenger side inside the cab. Not sure what the controls are, but guessing electric. There may be a door or actuator problem if the air isn't delivered to the selected positon...

[NotSteve]

The filters are ok and even when removed the air flow acts the same. I'm more concerned with the opening and closing of vents and why air comes out of places it shouldn't when other vents are selected.

Just wondering if anyone has fiddled with this stuff. Looks like it could be a pain.

[pdm]

sounds like a door isn't closing , a lot are plastic & sometimes the pivot breaks, or something falls into the vents etc.......& yes they can be a pain. Time remove the dash panels & start looking around.....

[marylandkw]

It is a royal pain for sure. But from what I gather you will not be deterred.

Once you open up the dash you will see ducts running from your defroster vents and dash vents and floor vents, where they all converge is where your problem is most likely at. You will have a flapper valve of some kind in there that is most likely not flapping.

Make it flap. Problem solved.

It will either be an electrically controlled flapper thingy or cable controlled. If it is cable controlled more than likely the cable is shot and needs to be replaced. If it is electrically controlled, the motor or servo is toast. Of course it could be a broken flapper.

I really would recommend you not goto a dealer or shop for this, while it is a simple repair you would likely incur many many hours of shop time as these tend to be a pain in the rear to get at.

[NotSteve]

Thanks Maryland, sound advise. Ya, I agree with going to the dealer on this one. They would see $$$$ signs. I haven't dived in yet but will make an attempt. I notice when the heat or AC is on the dash is either hot or cold. I looked a little once and noticed air coming out of ducts that connect so time to duct tape all of them while I'm in there.

I'll go right after the solenoid or whatever is opening and closing the vents. I think that would be a good place to start. Now that you mention it, I do remember something rattling around in there that stopped many months ago also.

The only thing that really bothers me is the AC. It should be blowing my face off and it's more like a light breeze.

[Rev.Vassago]

If your dash is getting hot or cold, it sounds like a simple fix - one of the hoses came off.

[NotSteve]

If your dash is getting hot or cold, it sounds like a simple fix - one of the hoses came off.

Ya, maybe your right. It does wicked hot and wicked cold and not much air comes out of the vent when the AC is on high. Down at the fan when I replaced it it would blow your head off.

[NotSteve]

I fixed my problem. The air filters were completely filled with dirt. I guess they don't last that long after being replaced.

The dash heating up and cooling off is from a duct connection that isn't that great. I'm assuming from the heat of the sun on the dash over time has caused it to warp. Not to worry, that's what duct tape is for!!!

[Rev.Vassago]

I fixed my problem. The air filters were completely filled with dirt.

I thought you said the filters were clean?

[tracer]

I had a similar problem on my 2004 International: when I switched on the DEFROSTER ONLY mode, the air was still going to the floor. Our shop ended up replacing the control panel of the A/C; plus .... the entire job under the dashboard (climate control unit?). The part itself was not that pricey, but the guy had to take apart the entire dashboard (I'm not kidding) and the labor charge was like 600 bucks

[Fredog]

I fixed my problem. The air filters were completely filled with dirt. I guess they don't last that long after being replaced.

The dash heating up and cooling off is from a duct connection that isn't that great. I'm assuming from the heat of the sun on the dash over time has caused it to warp. Not to worry, that's what duct tape is for!!!

put it on recirculate and leave it there, when you put it on fresh, it opens a door and lets dirt in

[NotSteve]

I really didn't think the filters were dirty. I just replaced them like 3 months ago but they were FILLED with dust to the max! I looked inside and it's a big grate right to the outside behind the air filter. I sort of thought they would have a better design then that like maybe a duct connected to a scoop that pointed down or something.

[Fredog]

I really didn't think the filters were dirty. I just replaced them like 3 months ago but they were FILLED with dust to the max! I looked inside and it's a big grate right to the outside behind the air filter. I sort of thought they would have a better design then that like maybe a duct connected to a scoop that pointed down or something.

that's what I was talking about, if you put it on recirculate, that door will close and you get all the dirt through your filter.

[Rev.Vassago]

that's what I was talking about, if you put it on recirculate, that door will close and you get all the dirt through your filter.

The air goes through the filter regardless of whether or not it is fresh air or recirculated air. Mine stays on fresh all the time, and I get the same dirty filters every few months. I pull out the filter, take it apart, and wash it. No sense in paying the inflated prices for filters when the old one can be reused.

[Fredog]

that's what I was talking about, if you put it on recirculate, that door will close and you get all the dirt through your filter.

The air goes through the filter regardless of whether or not it is fresh air or recirculated air. Mine stays on fresh all the time, and I get the same dirty filters every few months. I pull out the filter, take it apart, and wash it. No sense in paying the inflated prices for filters when the old one can be reused.

on a 379 pete, there is a door right behind the air cleaner that opens when you put it on fresh, this brings dirt straight to the filter, if you drive a lot of dusty roads, your filter will clog a lot sooner than of you put it on recirulate

[NotSteve]

I don't have a little door.

[Rev.Vassago]

I don't have a little door.

Did you also replace the filter in the sleeper when you did the one in the cab?

[Fredog]

I don't have a little door.

mine does and when I was hauling rock with it, the filter clogged up every day, I got looking and found the door that opened and drew the dirt from the road right into the filter. maybe they have changed it. it is kind of a stupid design.

[NotSteve]

Did you also replace the filter in the sleeper when you did the one in the cab?

I don't use the filter in the sleeper. I have a real APU and that filter stays pretty clean all the time