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2500 HD stuck in defroster mode

Discussion in 'Chevy Trucks' started by flykelley, Sep 16, 2011.

  1. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    Hi Guys
    My 05 chevy is stuck in default mode for the defroster, won't go anywhere else. Im being told its most likely the mode actuator. My truck has bucket seats and a center console. I can't seem to get to the top screw for this actuator. Not enough room to get a socket and rachet on it, can't seem to find a way to get a wrench on this screw. Any idea's? I have the dash half tore apart and can't seem to find any access to this area. Yes I have pulled the fuse and done the recal test and it didn't help.

    Thanks Mike
  2. Ctll

    Ctll Member
    from midwest
    Messages: 82

    did you have the batteries disconnected right before it start to have problems. If so turn everything of radio, fan, and unplug your phone charger. Disconnect both batteries for a few minutes and reconnect. Several we have worked on this fixed the problem. Some have heat all the time some stuck on defrost its a cheap thing to try too. Good luck.
  3. buddymanzpop

    buddymanzpop Senior Member
    Messages: 603


    Go at it from underneath the dash, pull the duct work out, there are two pieces of duct to remove, on is for the floor on the drivers side, it just pulls apart and is held in place with a plastic push tab,the other duct piece is in the center for the floor right over the drive train hump, this has a screw securing to the dash frame that must be removed, after these two pieces are removed you will have good access the the actuator. Just did an 04 less than a week ago.
  4. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    You can't get access to it with a factory CENTER console. If you are telling me to pull the seats and center console and then I will easy access to it then I'm all in. Also have had several guys tell me the screws for the actuator are 5.5mm. Mine are 8mm and I have owned the truck since it was new so I know they came from the factory that way.

  5. affekonig

    affekonig Senior Member
    Messages: 909

    #04-01-38-008: HVAC System Cannot Be Controlled Or Defaults To Defrost Mode (Repair HVAC Actuator Harness) - (Jun 17, 2004)
    Subject: HVAC System Cannot be Controlled or Defaults to Defrost Mode (Repair HVAC Actuator Harness)

    Models: 2003–2005 Cadillac Escalade, Escalade ESV, Escalade EXT

    2003–2005 Chevrolet Avalanche, Silverado, Suburban, Tahoe

    2003–2005 GMC Sierra, Yukon, Yukon XL



    • Some customers may comment that they cannot control the HVAC (heating, ventilation and air conditioning) system. Others may comment that the HVAC system defaults to the Defrost mode.

    • Technicians may find that the following diagnostic trouble codes have set:

    • B0229 Recirculation Actuator

    • B0414 Left Air Temperature Actuator

    • B0424 Right Air Temperature Actuator

    • B3770 Mode Actuator


    The HVAC actuator harness may contact a sharp edge on the instrument panel support brace, causing a rub through condition and a ground out of the actuator control and/or feedback circuits.


    Locate the HVAC actuator harness contact point shown by the arrow in the above illustration. The illustration is of the instrument panel with the instrument panel compartment door opened and folded downward. The actuator harness is located in the left side of the opening in the instrument panel.

    Technicians are to inspect the HVAC actuator harness for contact with the instrument panel support brace. Repair any damage to the actuator harness wiring and install protective plastic conduit over the harness. Install friction tape over the sharp edge of the instrument panel brace. Clear the diagnostic trouble codes and verify proper HVAC system operation.
  6. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    Thanks for the info but I have already seen this TSB and my harness isn't damaged by the dash. Im throwing codes 0414 & 3770.

  7. Mike,

    I have an '04 GMC 2500HD with buckets and console and I replaced the actuator from below JUST to the right of the console by the heater outlet. The screw was a ***** but I got it. After that, it was ten minutes start to finish to pop the actuator in. Hope this helps.

  8. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    Hi Dave
    The actuator of mine is on the drivers side above the heater tube. I can get a 1/4 drive socket on it but not a ratchet. I spent a couple of hours on my head trying to get that darn thing out but no luck. Looking for a 1/4 drive breaker bar but they seem to be hard to find. Maybe a 8mm nut driver that goes in a bit holder, and use a flat ratchet on the end of the nut driver. This one is a bit tough.:cry:

  9. 1/2tonthatcould

    1/2tonthatcould Member
    from MA
    Messages: 35

    there was recently a recall on this, anything to do with heat/ac in these trucks is a common issue
  10. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    The recall has to do with the wire harness coming in contact with a metal dash brace and damaging the harness. I have already looked at this harness and thats not the problem. Its a bad actuator with one screw in a very tough place to get to.

    Regards Mike
  12. 06Sierra

    06Sierra PlowSite.com Addict
    from Maine
    Messages: 1,329

    I believe the lower one on the right is the driver side temp control actuator. The pass side is higher up in the dash. On the left is the mode actuator.
  13. buddymanzpop

    buddymanzpop Senior Member
    Messages: 603

    I had no console to deal with, but maybe that's why the tech's at GM dealerships get 2-3 hours for that job, your mode actuator is the one to the left side of the console, also, when you do finally get to the re-installation stage there are two control levers that must be in the correct position on the big plastic control cam that the actuator moves,(this will most likely com out with the actuator) you may want to go the extra mile and pull the console because although it may take time it will save you from throwing tools in frustration, the actuator Motorman replaced is a temperature control actuator for the drivers side even though it is located just to the right of the console on the passenger side. Don't forget when you re-install that the top screw(which is the tough one to access) it also holds a plastic bracket for the actuator wire harness. Good luck. I think the screws where around 1/4 but I'm not positive on that one.
    Last edited: Sep 21, 2011
  14. buddymanzpop

    buddymanzpop Senior Member
    Messages: 603

    Talked to a Tech at the Chevy Dealership yesterday about your situation and he said "yes", pull the console for this job.
  15. flykelley

    flykelley 2000 Club Member
    Messages: 2,127

    Thank You