Vent issue

[19Ram150098]

98 ram 1500. 5.2L. My air/heat only blows from the defrost vents. I checked the outside vaccum hose that comes through the firewall and its good. My Dash is cracked pretty bad, so I ordered a dash mat to cover it. So I will probably chip away at the dash to be able to see the inside where the vacuum line comes through. Is there anything specific I should look for to fix the problem inside the dash?

 

[Fast69Mopar]

98 ram 1500. 5.2L. My air/heat only blows from the defrost vents. I checked the outside vaccum hose that comes through the firewall and its good. My Dash is cracked pretty bad, so I ordered a dash mat to cover it. So I will probably chip away at the dash to be able to see the inside where the vacuum line comes through. Is there anything specific I should look for to fix the problem inside the dash?

The first thing I would check is the vacuum check valve in the vacuum line that goes through the firewall.

Then I would remove the HVAC control head from the instrument panel and verify that you have a stable vacuum supply to the control head.

These control heads are known to have issues over the years. One of the main concerns is the mode door being unable to move due to vacuum loss in the control head. Just because you moved the mode switch to vent or floor doesn't mean the vacuum supply is being routed to the correct passageway in the controller.

If you don't own a hand vacuum pump, rent one from your local auto parts store and connect it to the main vacuum harness at the control head to see if each line holds a vacuum and operates each servo.

 

[19Ram150098]

So i looked under the dash and the yellow vacuum line goes from the control panel to the actuator looks good, if i move the actuator by hand it'll just stay on the vents. If i switch to defrost and back to vent it stays on defrost vents. Is it possible the actuator is losing suction?

 

[pacofortacos]

It is possible the actuator is failing.
If you can get to the actuator, try this - pull the vac. hose off of it, push it by hand like you did AND before you remove your hand from pushing it, plug the vac. port on the actuator with your other finger or something - if the actuator stays in the position you pushed it then it is ok, if the actuator moves while you are plugging the port on the actuator then it is going bad and you need one.

They can start to leak and not be able to pull in but will hold the in position once pushed there. Trying to rule that out.

You can also feel for vac. at the hose at the actuator if the truck is running.