FOR NAU81BLAZER, regarding Tailgate Glass

Discussion in 'The Garage' started by wubba_65, Sep 15, 2005.

  1. wubba_65

    wubba_65 Registered Member

    Jun 22, 2005
    Likes Received:
    Alberta, Canada
    I wanted to post in other thread, but I haven't ponied up the membership yet :doah: So I'll post in here, cause I want to help. #1 IS TO CHECK IF THERE IS A FUSE BLOWN IN YOUR FUSE BOX. It'll save a lot of time and Blasphemy if you do this quick check.

    Disclaimer - the following is only going by what wires are run to the tailgate, and what I think would make sense for a wiring system for the power tailgate. Feel free to correct if I'm wrong


    There are two different "harnesses" that go into the tailgate. One of these has a ground on it (for sure, the other I'm not sure about). The Key switch runs independent of ignition, and the dash switch is run through the ignition. I think that the dash switch controls the harness with the ground, while the key switch controls the other. One easy way to discern between the two is to unplug the harnesses for both switches (they only plug in one way, so no way of confusing them when you hook them back up). Get a voltmeter, and test which wire is live when you have the ignition off. I think that the one with the ground wire is the dash switch. Make sure that none of your grounds are corroded, and it still wouldn't hurt to pull them off, clean them up with a wire scratch brush and put them back on. Test to see if this improves things.

    The way that I see it working is there are two wires for each system (both should be live, one for up and one for down with each system). The wires coming from the battery to the tailgate for the key switch should both be live all of the time (grounded inside the tailgate and activate the motor when the key closes the circut to move window). The wires coming from the dash switch should be "dead" until the switch is activated either way. Test all of these (you'll need a helper to press the switch to test the dash harness). If all of the wires are good, then you know that the problem is somewhere after the connections to the tailgate, and you have elminated the biggest PITA (having to check all of the wiring from the harness to the switch, fuse panel and battery (for both harnesses)).

    If you don't get good power from all of the wires steps to diagnoss problems.

    1. For the Dash switch, pull it out and test the output of the switch (remember, ignition on, and "activate" switch in both directions). If you get good power coming out, there is a break in the wire between the switch and the plug at the back of the truck. If you don't get good power for one or both directions, test before (or inputs) into the switch. If you get good power to the switch (ignition on) then your dash switch is bunk. If you don't get good power to the switch, follow the wire back to the ignition or fuse panel (whichever it runs to, I'm not sure, haven't ever checked). If wiring is good, make sure that the fuse isn't blown AGAIN (if there is one, I'm sure there would have to be). If it isn't, trace it back to the ignition looking for broken/corroded wires.

    2. For the Key switch, the wires should run to the front of the truck, directly to the battery. Trace them back and see if there are any breaks in the wire. IMO it most likely isn't this, but you never know.


    This is where I haven't explored much, so it's all theory as to where the wiring goes from here. I would next test the wiring where it connects to the motor.
    1. If you are still getting good power from all four "live" wires, then there is something shot in your two way motor, and you need to replace that. To test this, you'll have to have your helper activate the dash switch and the key switch while testing the input to the motor (both systems should connect to one terminal here (ie both "up" wires should meet on the "up" terminal, and both "down" on the "down terminals").

    2. If you are getting power from the "key switch", and none from the "dash switch", I'm guessing you have some corroded wire or a break in your wire between the plug and the motor (good power to plug and none to motor mean disruption of the circut between the two). Trace wire between motor and plug and find the break/short

    3. To test power at motor from the "key switch" you'll have to have someone turn the key from outside while you test at the motor from the inside (window will have to be most of the way up, or else it will interfere). If you want to test with the tailgate open and window extended, don't forget to close the tailgate latches to bypass the safety switch. Test both directions (up and down) and if you are not getting power you have either a break/corrosion in the wire or a faulty key switch. If you are getting power from both but no movement, the motor is faulty.

    To troubleshoot a broken wire or faulty key switch, test power output at the switch, if you are getting power from both, then there is break in the wire running from the switch to the motor. If no power from switch, test power input into switch. Good power into switch from both wires (up and down) indicates a faulty switch, no power to switch (but good power to plug outside of gate) means a disruption of the circut between plug and switch, trace wires back and look for break. Again, look for the ground for this system inside of the tailgate, and make sure that it isn't corroded.

    The key is that they are two basically independent systems, and to work backwards when Diagnosing. I only start at the plugs because it is an easy way to find out if you are getting power to your tailgate without having to pull it all apart. Hope this helps, and I'm sure that I've left out some details, but use common sense and think about the flow of electricity through the system.


    1. two independent systems - Dash and Key
    2. check grounds and fuses
    3. test power at plugs - ignition on and activate switch for dash, key should be live all the time - if no power, work back wards. Dash, check switch, then fuse, then ignition, looking for breaks in wire between these devices
    4. if power good to plugs, test motor - no power from dash switch, broken circut, trace back wires. No key switch power, test at switch, then in front of switch. Check wires for breaks.



Share This Page