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No defroster

Discussion in 'Chevy Trucks' started by dzrick, Nov 14, 2007.

  1. dzrick

    dzrick Senior Member
    Messages: 110

    My heater and fan work great but nothing changes when I select defrost.

    Can anybody tell me what I should be looking at?

    Is this by chance the controller? If so is it something I should tackle myself?

    [​IMG]

    [​IMG]

    Rick
     
  2. dzrick

    dzrick Senior Member
    Messages: 110

    Almost forgot, it's an 88 Silverado if that makes a differance.

    Thanks in advance,
    Rick
     
  3. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    A repair manual may have the check out procedure for the switch and that part shown.
    If it does not go into it go to the library and look at a pro manual on the truck. Most large libraries have the Motors repair manuals some where.
     
  4. dzrick

    dzrick Senior Member
    Messages: 110

    I will see what I can find, thanks.
    Rick
     
  5. oakvillerex

    oakvillerex Member
    Messages: 65

    look for a broken vacum line under the hood or dash also there might be a flap jammed in the heater box
     
  6. dzrick

    dzrick Senior Member
    Messages: 110

    Do you by any chance know where this vaccum line starts and ends?
     
  7. chazmanian

    chazmanian Member
    Messages: 93

    Mine hafd the identical unit with the identical problem.

    Turned out to be an arm that attaches up above the acuator there. It comes off the connector really easily. Try and get way up in there with a flashlight yours may be the same.
     
  8. dzrick

    dzrick Senior Member
    Messages: 110

    Thanks, I'll check that out.

    It's not my dd so I'm a little slow to get around to working on it,
     
  9. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    chaz probably has the answer for you :)) ) Check the actuator over near the throttle pedal.. it has a small linkage that goes between the actuator and the defrost door that likes to break off. A flash light and a good set of eyes and you will be able to see it if it's not connected..

    Btw, The HVAC controls on an '88 full-size are all electric and/or mechanical...no vacuum at all.
     
  10. dzrick

    dzrick Senior Member
    Messages: 110

    I truely hope Chaz is right, I replaced the heater core years ago and didn't much care for that job. It was a PIA getting that back together:
     
  11. chazmanian

    chazmanian Member
    Messages: 93

    B&B is the one who steered me in the right direction....My big fat paws wouldnt fit up in there so I had my Father-in law with his little hands reach right up and reconnect er'.

    Worked like a Charm?

    How in the heck does a charm work anyhow?

    I bought a charm bracelet for the old lady and we still aint hit the lotto yet......:cry:
     
  12. sechracer

    sechracer Senior Member
    Messages: 478

    Ok, figures, I tore the heater box apart on mine this summer and couldnt figure out why things wouldnt change and it was the EXACT same problem.. Now my question is, does anyone know where to get the plastic clips for the linkage? my lower one is missing.........
     
  13. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Try the GM parts counter at a dealership. I have had them just give me something like that. It's not worth the 50 cents to print the Dealers embossed invoice. It would help if you knew what it looked like. They probably have a box with all the clips known to God / GM in it. They may even carry it in the HELP parts line at auto part stores.
     
  14. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    It's a very very common problem on them as the truck gets some age on it...

    Gm dealer will have the replacement clip....but I've fixed them with a wire tie before.