Overhead A/C blows warm when stopped,

Discussion in 'Heating & Cooling' started by dd350, Apr 9, 2019.

  1. dd350

    dd350 Active Member

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    '99 EB 5.4 -

    So normally when your A/C blows warm when you're stopped, it's because that A/C booster fan isn't working. So what if you don't have one?

    My rear/overhead A/C is all I've got at this point thanks to a failed blend door. If I put it on MAX A/C, turn the EATC speed to LO, and close the front vents I still get A/C out the ceiling vents - until I'm stopped at a light or in traffic. So how does the rear A/C work? Can this be addressed without fixing the blend door, or are the two somehow intertwined in a brilliant feat of beancounter engineering?
     
  2. 1955moose

    1955moose Full Access Members

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    It's possible it's either the Eatc unit acting up, or one of the blender doors. The Eatc units usually default to defrost, or in your case overhead vents. I'd do a diagnostic of your Eatc, and see if any codes come up.

    Sent from my N9131 using Tapatalk
     
  3. Yupster Dog

    Yupster Dog Full Access Members

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    I don't know about the 99 but my 02 EB when you put the front controls for the rear on low fan it lets the rear(2nd row) controls be active.
    That being said, Do you have 2nd row controls and what are they set to?
     
  4. dd350

    dd350 Active Member

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    I've got the separate controls (on the ceiling) for the 2nd row that I'm setting to HI and COLD and have the ceiling vents reversed to point forward. The front still blows across the heater core because of the broken blend door, but it's blowing it on LO into closed front vent doors so it's not noticeable. The overhead blows cold until I come to a stop and it gets warm, then when I get moving again it gets cold. What I'm wondering is whether this is something that can be fixed independently of the blend door (since that is such a major deal I'd rather not fix it) or if it is somehow caused by it.
     
  5. stamp11127

    stamp11127 Super Moderator Staff Member

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    What you are describing can indicate low system pressure in the ac. Check the static pressure on the ac system after it has been sitting for a few hours. The r134a pressure should be close to ambient temp. Once you have that check the low and high side pressures with the engine running - ac on max and compare to the chart in the link. If the system is low the static pressure will be less than ambient by a decent amount.

    http://acprocold.com/faq/r-134a-system-pressure-chart/

    Also make sure the fan clutch is working, condenser is free of trash, fan shroud is in place, radiator isn't blocked etc.
     
    Last edited: Apr 10, 2019
    1955moose likes this.
  6. dd350

    dd350 Active Member

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    Thanks stamp, I'll let you know how it turns out.
     

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