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99 dodge climate control

Discussion in 'Ram Trucks' started by Kingwinter, Jul 12, 2008.

  1. Kingwinter

    Kingwinter Senior Member
    Messages: 217

    alright boys, I have a problem for you.

    My 99 dakota it having a lil prob with the climate control switch. During the first 10-15 min, it is just on vent. When I turn the knob to AC or max ac or whatever, it doesnt do anything, and there is no resistance on the switch in doing do. After I wait for ten min and try it, I can here the "swish" of air, and can feel resistance on the switch. I took it apart, and see theres like vaccum cables hooked up to it.

    Now I have no idea about how these things work.

    Do I need a new switch, or is something else wrong?

    Thanks guys!
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Sounds like its losing its vacuum source initially after start up, as the "vent" position is the default position when no vacuum is present.

    A common cause of this is a defective check valve in the vacuum supply line under the hood, or the vacuum reservoir located under the cowl panel. The HVAC supply line should be tee'd into the large vacuum line going to the power brake booster. Temporarily bypass the check valve and the reservoir, if it now works correctly you can be sure its the reservoir or check valve causing the trouble.

    You can also check for supply vacuum right at the switch if you still have it out of the dash by simply starting the truck and placing your finger over each vacuum port in the vacuum hose connector.
     
  3. Kingwinter

    Kingwinter Senior Member
    Messages: 217

    is this the check valve?
    I checked the vaccum at the switch, and there was vaccum, although it wasnt very strong. I put the connector back on really tight and it's working for the time being, but if it stops working again, I'll replace the valve I think.

    vac line.jpg
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Thats the one King. That vacuum line heads across and into the firewall to the vacuum reservoir thats located under the plastic wiper panel and then into the HVAC switch Assembly. If you had vacuum when you checked it all is good for now but it may still be an intermittent problem caused by the check valve. At least if/when the next time it does it you'll know how to check it.

    Note: You mentioned that it didn't seem to have much vacuum when you checked it. There is a restrictor built into the check valve that limits the vacuum going to the HVAC controls, so you wont find a great deal of vacuum on that line. If you check it with an actual vacuum gage you should only see about 8 inches. Won't be full engine vacuum.
     
  5. Kingwinter

    Kingwinter Senior Member
    Messages: 217

    thanks man!