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Heated O2 Sensor wiring

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by SnackPack, Sep 8, 2005.

  1. SnackPack

    SnackPack 1/2 ton status

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    Forgive me if this has been dealt with, but I haven't seen any threads which detail the wiring of a heated O2 sensor. I purchased an ACDelco AFS-74 for < $50 at Autozone, but it has no wiring diagram.

    I understand I'll have to clip the plug that it came with and solder the old wire into one of the three on the sensor, but which one? Also, where would a good place be to wire up the (+) wire, which ever one it is?

    Thanks in advance
     
  2. Roz

    Roz 1/2 ton status

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    is this on ure 87' or what?
     
  3. SnackPack

    SnackPack 1/2 ton status

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    Yeah, sorry for the confusion. It's a TBI model.

    Adam
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    A couple of things:

    I don't think clipping the stock plug off is a good idea. The "signal" wire on the O2 sensors is not just normal copper wire, and it typically doesn't hold solder very well. IMO nothing other than a positive locking connector belongs on the O2 sensor, since it will eventually need replacing anyways. I'm sure there are other ways to do it, but finding the right connector in the wrecking yard shouldn't be too tough. Besides you could get enough wiring to do your swap too. You can buy the weatherpack (assuming that's what it is) depinning connector in the store, and Napa sells the pieces to "build" the weatherpack connectors. For one job, they don't cost much.

    Run the sensor off of the fuse panel, you can use a blade connector in one of the ignition hot 12V accessory ports from there, but I recommend one of the factory keyed/locking connectors, again plentiful as all get out in the wrecking yard.

    Wiring it up, not sure that I've seen it on here, but thirdgen.org's forums I have.
     
  5. 88sub4x4

    88sub4x4 1/2 ton status

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    Usually the wire used on the o2 sensors is not normal copper wire. I think it may be stainless, or some other metal, and soldering it will damage the wires and give you faulty sensor readings. If you must cut, then use a crimp connector, remove the colored plastic insulation, and heat shrink the connection to make it waterproof. Most heated oxygen sensors are supplied voltage, usually 5 to 8 volts depending upon the vehicle, from the PCM and as the sensor heats up, the resistance across the hating element changes, and the PCM gradually reduces the voltage and cuts it off completely once the sensor is warm. This whole process usually happens within 3-5 minutes depending upon ambient (outside) temps.
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    The AFS-74 is the most recommended heated O2 for early injection setups, I suspect that one of the reasons is that it works perfectly with 12 volts going to it.

    I'm not saying that some don't require different voltage, just that the early EFI systems have no way to regulate the voltage via ECM and I wouldn't worry about 12V to the AFS-74.
     
  7. 88sub4x4

    88sub4x4 1/2 ton status

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    I don't know much about that particular model, and retrofitting it into an older vehicle, I was just explaining how the newer ones operate since I wasn't sure what he was doing with that particular 02.
     
  8. SnackPack

    SnackPack 1/2 ton status

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    This one I got has one black wire and two white ones. How would I know which one is which? :confused:

    Adam
     
  9. SnackPack

    SnackPack 1/2 ton status

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    Nevermind, I figured out that the two white ones are non-polar for the heating. I assume one can go to 12V and the other to GND?

    Adam
     

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