need help with rear AC control system

Discussion in 'Interior' started by josh336, Apr 30, 2018.

  1. josh336

    josh336 TYF Newbie

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    ive got a 2000 Tahoe LT that has a inop. rear blower. The resistor was fried (i replaced). Im not getting signal from the purple wire to the resistor. I checked continuity to the 2nd row control unit from resistor (its good) , and continuity to the front control unit from 2nd row unit ,purple with white stripe, (its good too) all fuses are good but it seems the control system isnt getting power.
    big orange wire at resistor is 12v and will power blower if i jump black and purple signal wire. What should i check next.? thx
     
  2. M1Gunner

    M1Gunner Full Access Member

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    Depends. Do you have the new or old style system, is it rear a/c only or is it rear a/c AND heat...?
     
  3. josh336

    josh336 TYF Newbie

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    I'm not sure if it's new or old style. Could you explain the difference?
    This is the rear climate control that has the Ac and heat, it has two door actuators one for blend and one for direction.
     
  4. josh336

    josh336 TYF Newbie

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    I am getting 5v on the purple signal wire. I believe the purple wire gets its voltage from the blower motor resistor. And as that 5v is grounded, it sets the blower speed. So far I've established that
    1 blower works when purple wire is grounded.
    2 resistor is new and works as above.
    3 I have continuity on purple wire from resistor all the way to second row overhead control.
    4 purple/white wire from rear control to front control has continuity and voltage (5v).
    5. Purple/white wire voltage adjust from 0v-5v as the fan speed knob is turned on the front control unit.
    6. Purple wire voltage from rear overhead control unit doesn't vary with rear knob adjustment and front control unit on (Rear) setting. Stays 5v
    7. Both front and rear blend and direction servos work to control the rear air temp and direction as they should.

    I'm leaning towards the rear overhead unit is bad, but I bought another unit (used) and it isn't working to turn fan on either. It's possible the used unit is also fried. Any input is appreciated. Maybe some way to bench test the rear control unit to verify it is inop. Thx again.

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  5. josh336

    josh336 TYF Newbie

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    Thanks for all the help. No sarcasm there. It was the rear overhead control unit. Apparently the used unit I got was fried too. I found a new old stock one and installed it today. All is working.


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