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Heater/HVAC Air only goes to Defrost Vent

Posted

Hi All,

 

I changed the resistors in my HVAC system and solved the fan speed issue.  I decided to change the fan/motor as well and now there is no air coming out of the dash or floor vents only out of the defrost vents by the windshield.

 

Any ideas are welcome.

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  • IBMobile
    IBMobile

    Check for vacuum at the hose at the right out side fire wall. 

  • dripley
    dripley

    Yes. It goes thruright where the AC linez pass thruu the fire wall. Mine broke there some years back. It is small 1/8" plastc lne. IIRC it has a fitting on lt. Be careful heat from the exhaust made mi

  • dripley
    dripley

    If you knocked the vacuum line off the pump yes, both would fail. The vacuum line to the hvac runs acroos the fire wall and thru on the passenger side. It is possible for that line to fail and the 4wd

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  • Staff

Do you have air flow through the defrost or floor vents? 

If no, then the fan motor is running backwards.  

  • Author
2 minutes ago, IBMobile said:

Do you have air flow through the defrost or floor vents? 

If no, then the fan motor is running backwards.  

I have air through the defrost vents only.

 

I checked the new fan to make sure its going the same direction as the old fan.  I heard that might be an issue with the new aftermarket fans so I checked that before put it in.

  • Author
1 minute ago, IBMobile said:

Check for vacuum at the hose at the right out side fire wall. 

Okay will do when I get some daylight again.  Thank you!

 

2 minutes ago, IBMobile said:

Check for vacuum at the hose at the right out side fire wall. 

By right side you mean passenger side correct?

1 hour ago, leety said:

 

 

By right side you mean passenger side correct?

Yes. It goes thruright where the AC linez pass thruu the fire wall. Mine broke there some years back. It is small 1/8" plastc lne. IIRC it has a fitting on lt. Be careful heat from the exhaust made mine brittle and it broke. Not much to work with either.

    • Like 1
    • Author

    Okay so rookie lesson learned.  Now I know, no engine running, no vacuum pump pumping, no door heater/HVAC actuation.  Derp.

     

    Thanks everyone.

    27 minutes ago, Mopar1973Man said:

    Yup. No problem. 

     

    2003 and up are all electric stepper motors. 

    2002 and down is all vacuum driven.

    Mine is electric. I had to reset it with a 9 volt battery that came with the heater treater metal part. You do mean the motor thatnoperatesmthe blend door right?

    • 9 months later...
    On 3/9/2020 at 9:49 PM, leety said:

    Hi All,

     

    I changed the resistors in my HVAC system and solved the fan speed issue.  I decided to change the fan/motor as well and now there is no air coming out of the dash or floor vents only out of the defrost vents by the windshield.

     

    Any ideas are welcome.

    Same thing just happened to me today, it worked earlier but stopped suddenly. Would that vacuum line effect 4x4 because it still works?

    If you knocked the vacuum line off the pump yes, both would fail. The vacuum line to the hvac runs acroos the fire wall and thru on the passenger side. It is possible for that line to fail and the 4wd to stil work. But mine is an 02 and could be different. My advise would be to check the vacuum lines out from the pump to the manifold and the branch lines to their terminations. My line faied to the hvac near the firewall, then a bit later somewhere under the dash.

     

    I have to admit l am not up on the vacuum system routing on a 98.5. 

    Edited by dripley

    • Like 1

    thanks for the help looking into it

    If you check out the down loads section I think we have a FSM for your truck available for down load.

    4 hours ago, dripley said:

    If you check out the down loads section I think we have a FSM for your truck available for down load.

    thanks it started working again?? im confused but definitely need that


     

    It would be good just to look over your lines and fittings. They do rot with age. Just start at the vacuum pump and work your way back. Not much to it.

    • Like 1
    • Owner

    Yup. @dripley is right. The rubber pieces do fail over time. The only vacuum used is typically the cruise control (auto) and the HVAC controls (all).Then the rare type like me vacuum exhaust brake (optional).

    • Like 1
    • Author
    14 hours ago, Manny said:

    Same thing just happened to me today, it worked earlier but stopped suddenly. Would that vacuum line effect 4x4 because it still works?

    I let the truck run and then tried it it was fixed after I let the truck run.  I guess the vaccuume pressure just needed to build up.

    • Owner

    You've got a leak some where. Double check your CAD axle system really common for vacuum leaks in the CAD system. 

     

    Vacuum should be instant. No waiting to build. Vacuum leaks will make everything slow to react. 

    • Like 1
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    Welcome To Mopar1973Man.Com LLC

    We are privately owned, with access to a professional Diesel Mechanic, who can provide additional support for Dodge Ram Cummins Diesel vehicles. Many detailed information is FREE and available to read. However, in order to interact directly with our Diesel Mechanic, Michael, by phone, via zoom, or as the web-based option, Subscription Plans are offered that will enable these and other features.  Go to the Subscription Page and Select a desired plan. At any time you wish to cancel the Subscription, click Subscription Page, select the 'Cancel' button, and it will be canceled. For your convenience, all subscriptions are on auto-renewal.