2007-2012 (X164) Heat won't turn off

Discussion in 'GL-Class' started by Kdrinkh2o, Jun 7, 2017.

  1. Kdrinkh2o

    Kdrinkh2o New Member

    My 08 GL450 climate control system is stuck on full defrost heat mode. It began with the blower turning itself on about 2 or 3 minutes after the car was shut off. This would cause a dead battery in the morning, however when the car was running, the controls worked fine. I could control the temp and blower speed, switch back and forth between heat and ac, vent control, etc. After a week or two of this, it began having intermittent trouble switching between temps, then all of a sudden the blower went to full speed and all controls stopped working with the setting seemingly stuck on defrost (heat comes out by windshield and side vents). I actually tried a different control head that I found on EBay with the exact same behavior. Is there a relay or computer module that could be causing this?
  2. Kdrinkh2o

    Kdrinkh2o New Member

    Update...based on my research, it seemed like the heater control valve might be the culprit so I purchased a new one. When I finally got the old one removed from the back of the engine, I discovered that the old part has no valve. The part I purchased has an electric valve with wired connection but the old part has just aplate on top.
    Any kind of help with this would be greatly appreciated!

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