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04 sierra no #1 and 2 on the heater/AC

Discussion in 'Truck & Equipment Repair' started by samjr, Jun 18, 2009.

  1. samjr

    samjr Senior Member
    Messages: 481

    1 and 2 dont work and if i put it on the vents it gos to the floor do i need and new switch unit:confused:
  2. Bigfoot Brent

    Bigfoot Brent Senior Member
    Messages: 202

    I've had the same problems on two '05 Sierra's at work. Lost fan speeds 1 and 2,then 3, then all. I replaced the resistor for the heater fan motor as well as the 7 wire plug to it, as the plug had started to melt. It is located by the passengers feet. Fan speeds 1 to 4 work great now, but 5 doesn't work at all, so I'm still scratching my head on the problem. Oh, the parts cost a fortune from GM (near $300) so try to see if the resistor and plug are available through the aftermarket.
  3. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    You may or may not have more than one issue causing this problem Sam. With a good scanner it could be easily narrowed down but here's the cliff notes...

    Your lack of all blower speed settings can be caused by one of three things. Most common is a defective blower resister (as was already mentioned). Second most common (on the '03-'05 model year trucks especially) is a chaffed wire or wires in the HVAC harness that runs behind/across the dash between the HVAC control module and the blower resistor. If you pull the glove box door out you'll see the harness and can check it for any abrasion (see pic below). Third (and not too common) is a defective HVAC module.

    Now, the lack of air direction through the selected outlets also has three possible possibilities. There has bee a TSB out for years that included a reflash of the HVAC module to correct an over travel condition of the blend doors. When a blend door over travels it will set a DTC code in the HVAC module and when that specific blend setting is again selected (the same one that set the code in the first place) it will cause the door to go to a "default" setting rather than the one you selected.

    If you disconnect the battery for a minimum of 5 minutes and then retry the dash vent setting (See post #2 here) it then works fine (even temporarily) then the reflash should solve the air direction issue. If disconnecting the battery doesn't help, then you've got a defective HVAC head module.

  4. Truck207

    Truck207 Member
    from Maine
    Messages: 91

    My uncle had the same problem in his 2005 Chevy 3500. He lost setting 1 and then he lost all 1-5. He took it to the dealer and of course it was already out of warranty, they replaced the whole module for around $300. He asked if it was a recall, because they told him they have seen this problem often, but they said GM has not made a recall for it.
  5. 06Sierra

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

    Check rockauto.com or gmpartsdirect.com. I put a resistor in my 04 Yukon last summer. I don't remember the cost but it was much cheaper than the dealer. I also put a temp control actuator in this summer for $130 from rockauto. The dealer wanted over $250 for that!
  6. samjr

    samjr Senior Member
    Messages: 481

    thanks all and B&B I disconnected the battery for 5 minutes and then dash vent setting are AOK but B&B is this a temp fix or is it something i got to fix? And went to the dealer and got a defective blower resister for $65 so anion thanks all tymusic
  7. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    If doing the battery disconnect procedure fixed the air position issue (even temporarily like I mentioned) then yes the re flash will fix it. Have the service writer take a look at bulletin # 06-01-38-003. It pertains specifically to door over travel conditions setting DTC codes causing incorrect/commanded door functions.
  8. Clint S

    Clint S Senior Member
    Messages: 280

    NAPA has a resister that works, but is not an exact fit. I had to modify the bracket that holds it in, but it works fine and was only $60