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Heater/ 4wd Problems with a 97 3500

Discussion in 'Chevy Trucks' started by R.M Hanson, Nov 25, 2007.

  1. R.M Hanson

    R.M Hanson Junior Member
    Messages: 24

    I've got a couple of problem with my truck, and thought I'd ask for some help before I start thowing parts at it. My heater contols quit working the other day, and only work on high, and not 100% of the time. I replaced the entire contol module in the dash, thinking the switch was bad, but the problem is still there. The second problem is the 4wd not engaging. It is a floor lever on this truck, and when shifted to 4wd, the ABS light comes on, and the front axle will not engage. I just changed the thermal actuator early this spring, so I hope it's not bad again. This problem didn't occur untill the heater problem, so I don't know if it's some kind of wiring related issue, or two separate problems. Let me know what you guy think, and I'll try and figure this thing out. Thanks.
  2. haejinjoe

    haejinjoe Junior Member
    Messages: 28

    I would suggest looking at the blower resistor for the blower only working on high intermittently. It likely needs to be replaced. Sorry no help on the 4wd question.
  3. Duncan90si

    Duncan90si Senior Member
    Messages: 602

    He's right. You have to remove the glove box to get to it. Its located on top of the air box/duct under the dash. Its a little bit of a pain to change. They usually cost under $20 at your local parts store.
  4. MickiRig1

    MickiRig1 PlowSite Veteran
    Messages: 3,617

    Get under the truck and see if you have power to the actuator. Might of blown a fuse or a connector plug with the wires to it and the heater blower have come loose. Check your ground wires under the hood too. Protect connections with Dielectric grease.
  5. R.M Hanson

    R.M Hanson Junior Member
    Messages: 24

    Hi guys, I just picke dup a new resistor for the blower motor, so I'm going to work on replacing it this afternoon. I also decided to buy a posi-lock kit for the 4wd, it should be here in a couple of days. I'll just have to do some looking and try and figure out what really happened to make it not function properly, to ensure nothing else is damaged. Thanks, and I'll let you know how it comes out. Untill then THINK SNOW!!!!!!!!
  6. ABES

    ABES PlowSite.com Addict
    from MN
    Messages: 1,322

    i had the same problem your having with the heater i replaced the resistor and that wasnt it. it ended up being the HVAC module if i remember right.
  7. DJ Contracting

    DJ Contracting PlowSite.com Addict
    Messages: 1,392

    I just replaced the resistor in my 93" it also did not work in the lower speeds and it took care of mine, however with the blower working intermittent you could have a two fold problem the resistor cost me $17.00 good luck.
  8. ppease

    ppease Member
    from Maine
    Messages: 55

    You will love the Posi-lock. I had one on my 89, need to get one for my 97. You can use 2-Lo, which is handy when backing a heavy trailer. When roads are spotty, leave the front axle in, just use the T-case lever when you need 4wd. No lines, no waiting.
  9. R.M Hanson

    R.M Hanson Junior Member
    Messages: 24

    I finally figured out my problem. After replacing the resistor, and the HVAC module, the problem was still there. Talk about discouraging, so I called my dad to help out. After spending some time with a multimeter, We determined that everthing was good from a wiring standpoint. The problem actually turned out to be the ignition switch. GM runs the HVAC, antilock brakes, 4wd, and cruise are all run off of the same power feed. The switch was sending low amps to this circuit, causing things to work eraticlly, or not at all. Wiring can be such a pain sometimes, but at least it's fixed now. Just though I'd let you know how it came out. I'm also working on installing the posi-lock kit this afternoon, it should make it a lot more depndable than the thermal actuator. Sometimes I wish things were simpler, like a 70's truck, but then I drive one and my mind changes back pretty quick.