Most everyone here has likely come to the point of cursing Jeep for making a motorized rear window that MUST be rolled down in order to open the tailgate. And isn't life grand when something in that circuit or process fails.
In troubleshooting my own tailgate window issue, I have became very familiar with how this circuit works and have copied some of my replies in other threads to here:
The number one cause of TG Window failure is a little plastic switch inside the tailgate. It serves as the Grand Central Station for all of the wires from the front dash switch, rear key switch, and window motor (see details below)
A - Main power 12v supply (always on), this is also tied to F (no-wire) via a brass plate on the switch
B - one of the 2 wire feeds from the front dash switch
C - Wire lead going to the motor actuator
D - Wire lead going to the motor actuator
E - Other of the 2 wire feeds from the front dash switch
F - See A
Here's how it works:
Using the Front Dash Switch (connections B, C, D and E)
When resting, the front switch has the two leads going to the rear tailgate window switch Fully grounded
The rear switch (when resting) connects the two feeds from the front switch leads to the actuator (B-D & C-E). As they are both grounded, nothing happens.
When you move the front switch up or down, one of the 2 leads becomes energized, thus passing a + - current to the actuator, depending if it is +- or -+ determines the motor direction (up or down).
Using the rear key switch (connections A, C, D and F)
The switch has a post that is pushed one way or the other when you turn the key in the rear lock. One way connects A-C and B-D, the other way connects E-C and F-D. Because the hot feeds are opposites (A and F), and the front switch (resting) grounds B and E, you can see how the up and down are controlled by the different +- feed to the motor.
Heres the fix:
So, your plastic switch has finally broken down.. If you've started doing your homework, you'll be finding that an OEM switch is impossible to find (discontinued) beyond one in another Jeep, which could fail at any point.
Check out this site, it gives you perfect instructions on how to modify a modern common "momentary on" (aka MOM) switch to work as a reliable and improved solution, they even give the part number of the switch!
DO NOT USE THE PART NUMBER PROVIDED IN THE IPENDIA THREAD ABOVE, you will no longer be able to use the dashboard tailgate window switch if you do. Instead, order a Carlington Switch (part no 6GER5M-73) from onlinecomponents.com. These switches are manufactured on order, so it will take 5-6 weeks to arrive and cost ~$10-15 for the switch plus shipping.
EDIT:
When removing the rear key cylinder in order to remove the rear tailgate switch, you will need to do one of the following:
A. Acquire a hollow Star/Torx tool as there is a little post in the star well on the screws (using a unique tool makes it harder for the would be thief to remove your lock). Sorry, I don't know the precise size off hand.
B. Using a creative tool (I used the engraving bit on my dremel), grind down the post. Be careful not to let the tool slip around and damage the Star pattern in the screws. I figure if someone wants in bad enough to remove the lock, they'll just break a window anyway.
I also discussed with a gentleman, an issue where his rear lock switch worked in moving the window, but the front wouldn't. Here was my reply:
If your rear lock switch works, then everything inside your tailgate and wiring must be fine. In this scenario the problem has to be in the front switch itself, or the power feed to the front switch.
In order for the rear switch to work, it relies on the two wires (brown/tan most commonly) coming from the front switch being grounded and everything in the rear tailgate being in good contact. IE, your rear switch won't work without the grounded feeds from the front.
The only issue that makes since, is that when you try to use the front switch either:
A. The power feed going to the switch is dead (blown fuse possibly because this is a separate feed from the 12v that goes to the rear switch).
B. The front switch itself has failed, causing the power feed to not make contact when you move the switch up and down.
Here's how the front switch works.
Resting - Both feeds going to the tail gate are grounded.
Up - One feed to the tailgate remains grounded, the other becomes energized from the hot wire in the front switch harness.
Down - The exact same as up, except, of the two wires going to the tailgate, the hot/grounded lines are opposite from the up. What was grounded when pushing the switch UP, is now live; and what was live when pushing the switch UP is now grounded.
I would first test by pulling the wiring harness off of the front switch, you should find a single point on the harness with a red live wire coming in (or 2 wires sometimes, but they connect at the same single point in the harness), this point should be 12v.
For example, the front tailgate switch wire harness on my 82 has 2 red wires (12v) coming in to the harness at a single point.
2 black wires (grounded) coming in to the harness at a single point.
1 brown wire going to the tailgate.
1 tan wire going to the tailgate.
Giving a total of 4 separate contacts
The brown and tan wires are grounded when the switch is resting.
If I move the front switch up, one of the brown/tan wires becomes 12v live. The other one if I move the switch down.
The only exception to this, would be if the rear switch (when resting) is failing to connect the two feeds from the front switch to the motor leads (see the diagram above), but is still capable of making contact when the post in the rear switch is pushed up or down via the rear key mechanism. If all electrical troubleshooting of the front switch appears to be in proper order, then replacement of the rear switch is required, see the link above.
The key point to know here, is that the front switch has its own 12v feed, and the rear has its own separate 12v feed. Often, these are on 2 separately fused circuits, so just because one is hot, doesn't mean the other is.
In troubleshooting my own tailgate window issue, I have became very familiar with how this circuit works and have copied some of my replies in other threads to here:
The number one cause of TG Window failure is a little plastic switch inside the tailgate. It serves as the Grand Central Station for all of the wires from the front dash switch, rear key switch, and window motor (see details below)
A - Main power 12v supply (always on), this is also tied to F (no-wire) via a brass plate on the switch
B - one of the 2 wire feeds from the front dash switch
C - Wire lead going to the motor actuator
D - Wire lead going to the motor actuator
E - Other of the 2 wire feeds from the front dash switch
F - See A
Here's how it works:
Using the Front Dash Switch (connections B, C, D and E)
When resting, the front switch has the two leads going to the rear tailgate window switch Fully grounded
The rear switch (when resting) connects the two feeds from the front switch leads to the actuator (B-D & C-E). As they are both grounded, nothing happens.
When you move the front switch up or down, one of the 2 leads becomes energized, thus passing a + - current to the actuator, depending if it is +- or -+ determines the motor direction (up or down).
Using the rear key switch (connections A, C, D and F)
The switch has a post that is pushed one way or the other when you turn the key in the rear lock. One way connects A-C and B-D, the other way connects E-C and F-D. Because the hot feeds are opposites (A and F), and the front switch (resting) grounds B and E, you can see how the up and down are controlled by the different +- feed to the motor.
Heres the fix:
So, your plastic switch has finally broken down.. If you've started doing your homework, you'll be finding that an OEM switch is impossible to find (discontinued) beyond one in another Jeep, which could fail at any point.
Check out this site, it gives you perfect instructions on how to modify a modern common "momentary on" (aka MOM) switch to work as a reliable and improved solution, they even give the part number of the switch!
DO NOT USE THE PART NUMBER PROVIDED IN THE IPENDIA THREAD ABOVE, you will no longer be able to use the dashboard tailgate window switch if you do. Instead, order a Carlington Switch (part no 6GER5M-73) from onlinecomponents.com. These switches are manufactured on order, so it will take 5-6 weeks to arrive and cost ~$10-15 for the switch plus shipping.
EDIT:
When removing the rear key cylinder in order to remove the rear tailgate switch, you will need to do one of the following:
A. Acquire a hollow Star/Torx tool as there is a little post in the star well on the screws (using a unique tool makes it harder for the would be thief to remove your lock). Sorry, I don't know the precise size off hand.
B. Using a creative tool (I used the engraving bit on my dremel), grind down the post. Be careful not to let the tool slip around and damage the Star pattern in the screws. I figure if someone wants in bad enough to remove the lock, they'll just break a window anyway.
I also discussed with a gentleman, an issue where his rear lock switch worked in moving the window, but the front wouldn't. Here was my reply:
If your rear lock switch works, then everything inside your tailgate and wiring must be fine. In this scenario the problem has to be in the front switch itself, or the power feed to the front switch.
In order for the rear switch to work, it relies on the two wires (brown/tan most commonly) coming from the front switch being grounded and everything in the rear tailgate being in good contact. IE, your rear switch won't work without the grounded feeds from the front.
The only issue that makes since, is that when you try to use the front switch either:
A. The power feed going to the switch is dead (blown fuse possibly because this is a separate feed from the 12v that goes to the rear switch).
B. The front switch itself has failed, causing the power feed to not make contact when you move the switch up and down.
Here's how the front switch works.
Resting - Both feeds going to the tail gate are grounded.
Up - One feed to the tailgate remains grounded, the other becomes energized from the hot wire in the front switch harness.
Down - The exact same as up, except, of the two wires going to the tailgate, the hot/grounded lines are opposite from the up. What was grounded when pushing the switch UP, is now live; and what was live when pushing the switch UP is now grounded.
I would first test by pulling the wiring harness off of the front switch, you should find a single point on the harness with a red live wire coming in (or 2 wires sometimes, but they connect at the same single point in the harness), this point should be 12v.
For example, the front tailgate switch wire harness on my 82 has 2 red wires (12v) coming in to the harness at a single point.
2 black wires (grounded) coming in to the harness at a single point.
1 brown wire going to the tailgate.
1 tan wire going to the tailgate.
Giving a total of 4 separate contacts
The brown and tan wires are grounded when the switch is resting.
If I move the front switch up, one of the brown/tan wires becomes 12v live. The other one if I move the switch down.
The only exception to this, would be if the rear switch (when resting) is failing to connect the two feeds from the front switch to the motor leads (see the diagram above), but is still capable of making contact when the post in the rear switch is pushed up or down via the rear key mechanism. If all electrical troubleshooting of the front switch appears to be in proper order, then replacement of the rear switch is required, see the link above.
The key point to know here, is that the front switch has its own 12v feed, and the rear has its own separate 12v feed. Often, these are on 2 separately fused circuits, so just because one is hot, doesn't mean the other is.
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