Wild Vents

[Meatball12]

Im having a similar problem. Air only blows from floor vents no matter the position. But it doesnt blow hot or cold just ambient air temperature... any ideas??? No vacuum leaks found, will check valves cause this? Or is this more of a blend door issue?

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Sounds like the blend door or the selector knob. One way to check is with the truck idling, disconnect the vacuum line for the accessories and see if it changes to Defrost like its designed to do. If it changes; my money is on the Knob. If it stays the same your blend door may be stuck.

As far as the Temp issue I have no clue. Did it work before?

 

[916king916]

Temp hasnt work since I bought the truck about a year ago... with the glove box out I can see what im assuming is the recirc door open on max a/c on the knob and then closes on all other settings. Not sure if that helps

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[Meatball12]

The first thing I would try would be to replace the controls. You can usually find one at a scrap yard nearby for a few bucks or on Ebay for a bit more but in better shape.

But before you do anything I would check to make sure:
1- Your AC is charged
2- You have fluid going to the heater core and that it is not clogged
3- That the temp blend door moves with the Temp knob. (Just unscrew the motor and watch it as you turn the Temp knob)

and to clear a few things up.
Blend door= temp control
Vent door= where the air comes from

I mixed these up in my last post

 

[916king916]

The first thing I would try would be to replace the controls. You can usually find one at a scrap yard nearby for a few bucks or on Ebay for a bit more but in better shape.

But before you do anything I would check to make sure:
1- Your AC is charged
2- You have fluid going to the heater core and that it is not clogged
3- That the temp blend door moves with the Temp knob. (Just unscrew the motor and watch it as you turn the Temp knob)

and to clear a few things up.
Blend door= temp control
Vent door= where the air comes from

I mixed these up in my last post

Im not so worried about the a/c working or heat right now. im more focused on getting air to blow from my other vents mainly defrost vents. I figured once I can get the air to blow where its supposed to ill start diagnosing the hvac system.... or am I wrong to think this way?

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[916king916]

Also another thing I wanted to mention was all the pictures Ive seen online show the blend door actuator underneath the glove box held in by two screws. But I cant seem to find mine all I see is the blower motor and some resistor or something theres not even holes where it would/should be mounted just a rod that sticks out from the box

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[Meatball12]

So then I would try disconnecting the accessory vacuum line under the hood and seeing if the airflow changes locations. Ill try to snap some pics of the exact line in question in the morning.

As far as the blend goes. I'm not sure but I remember hearing that some trucks used a mechanical linkage instead of a motor to control the blend door. However I may be wrong so don't hold me to it.

 

[916king916]

So I realized that my blend door actuator is just missing along with the little plastic pieces the screws mount to for it. I had another known working truck to compare it to and realized quickly that its gone... next question is how can I attach a new actuator without the holes to mount it to, and is that gonna solve my vent problem or hot/cold air problem?

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[916king916]

Btw thanks for the feedback. I would really like to get this solved. Also I realized I never mentioned this is a 98 1500 5.9L

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[Meatball12]

Yes this should solve your Temp issue. As long as there is no issue with the AC system or heater core.

Vent door is going to be a separate problem.
IN the Diagram. The check valve on the left should be connected to a thin vacuum line that leads into the Cab. Disconnect that to see if you vent changes to defrost.

 

[Meatball12]

As far as Mounting the Actuator. Can you post a pic of what you are dealing with, it will be easier to visualize. Also, as a possible solution without seeing anything, Gorilla glue is a magical thing.

 

[916king916]

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[Meatball12]

So it looks like you are not supposed to have a motor. That looks nothing like mine without the motor attached. I hear that some trucks were not operated by a motor and had a mechanical linkage between the knob and blend door. It seems like that is the case but Im not 100% sure. We would need someone else that has a 98 to weigh in.

 

[916king916]

I work at firestone and we had an identical 98 in the other day it had one, thats why I said it was missing. The other one had plastic coming down about an inch where those two spots are other than the rod that the actuator mounted to, it looks like on mine they were possibly broken off with the actuator im assuming??? I still havent checked the check valves you mentioned either. Im gonna do that next and see what changes.... as far as the part, I called oreillys and carquest they said it didnt exist and the dealership said they have the same actuator for all doors $44... Im just unfamiliar with this system and wanna get clear whats what before i start throwin parts at it

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[Meatball12]

Here is what I have. It looks like on your truck the mounting points never existed. Maybe the motor was mounted on top? Unfortunately, I think there is a dash pull in your future if you really want to get to the bottom of this.
*Don't know how to rotate the pic. its correct on my comp*

 

[916king916]

Looks like you're probably right. Not sure where to go from here??? Smh

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