Hoping for some help WRT the tailgate glass in our 1988 Bronco. The window just stopped rolling up and down the other day. Got it in the garage and taken apart, the motor had those stupid deteriorated plastic nuts inside that we replaced with metal nuts. Then come to find out that neither switch will operate the rear window. Hooking the motor directly to 12V causes it to work fine, so we know the motor isn't the issue. With the test light in the other end of the plug and crossing the two poles we were able to get the test light to light up with the key switch on the tailgate in one position (not sure if up or down). Does anyone know how this wiring works? I assume the current flow (positive and negative) are switched to make the motor go up and down. We've got no power from either the dash switch (brand new Motorcraft replacement) or the key switch on the tailgate (has always worked). It seems awful curious that both switches would go bad at literally the same time. I've included a photo of the wiring diagram shown in my Haynes manual.



Yeah I don't really know how to read wiring diagrams so any help would be nice. There are some wires that look spliced together with butt connectors from the PO but they've always worked. I should add that I don't think its a fuse issue as other components tied to the two fuses in the wiring diagram work fine.

 

I had a similar problem a few weeks ago and it was the safety switch on the driver side latch. Usually you can push on the driver side of the tailgate to get it to latch properly and the dash and key switches will work again. That didn't work for me so I had to remove the window motor from inside the rig with the tailgate and window in the up position. I decided that I wasn't doing that again so I bypassed the safety switch. Hopefully trying to push the tailgate closed and getting it to latch better works for you.

 

Yes the safety switch is the red -yel wire and tan - blk wire labeled tailgate window sw. (bottom of diagram )This safety switch prevents the window from operating if gate is opened .When operating your tailgate its best to start the truck Good luck TR

 

Yup:

https://www.ford-trucks.com/forums/1...em-solved.html

 

Thanks for the help y'all. I'll definitely have to check that safety switch out. Unfortunately this weekend we have to go to Pennsylvania for a funeral so I won't be able to take a look till mid-week at the earliest.

I'll be sure to let you all know what happens!

 

Thanks Evan! Not all problems are the same. And if you come back to post up your fix, it just makes it easier for all who find your thread later. I will tell you this, no vehicles have a tailgate window now. And having a properly functioning rear window on the Bronco is truly a joy. And it is achievable.

 

The wiring for the tailgate window motor takes some time to comprehend fully. A person has to get in the mind frame that the chassis ground is not used in the middle of these circuits, it is at the end after the switches. If you haven't found this site yet, it is like the tailgate bible.
1983 Ford Bronco Tailgate Tech pictures, videos, and sounds | SuperMotors.net
You can use a jumper to bypass the tailgate safety switch if it is not working when the driver's side tailgate latch is closed.

 

So..... I tried my best to jump the connector for the safety switch. First I unplugged the connector and then used a spare piece of wire as well as a paper clip. I tried to jam the wires as far into the connector as possible (the bit I had unplugged, not the interlock mechanism itself) and then I used the wire. Each time I tried to operate the motor via the key switch and got nothing. Not sure if I'm not doing it right or if something else could be at fault. Motor works via a battery and two wires attached to the motor plug.

 

Evan, see my thread, it is likely the mechanical closer. If you can figure out the electrical to jump it you are better than me. So I suggest you move the mechanical closer to the correct position when the tail gate is down and see if the tail gate window goes up or down with the key in the tail gate lock.

P.S. it will break if you extend the window very far at all.

 

Tim: it very well may be a mechanical issue in addition to another which I've uncovered.

I have power to the safety switch in the "Down" position only - that is the down position on the dash switch and what I guesstimate to be the down button on the tailgate switch. Neither "Up" position gives any juice to the safety switch. With that in mind, this seems to be another issue which needs to be resolved before the greater issue is dealt with. I can't see both switches failing, there has to be an issue with the "Up" circuit.

Once I have power to the safety mechanism in both the up and down positions and have jumped the plug and gotten the motor to work properly, I'll check if the safety mechanism itself is misaligned.

 

@Bruners4 and @Franklin2 can you help? I have wired house 3 way and even 4 way wall switches for in ceiling lights, but it always torques my mind a little when I do them and I have to stare at the wiring diagram and keep rechecking it to get it right. The fact that the ground does not go from the switch but is a wire connecting the two switches is interesting. I assume it is because the "ground" wire alternates between being a ground wire or a hot wire depending upon what position the window is in. I.e., these are likely both Double Pole Double Throw switches like what I believe control the passenger side window from both the passenger side and the driver's side doors.

Double Pole Double Throw (DPDT) Switch

Evan, the real brainyacks on electrical here are in the following subforum. You may want to ask the moderator to move your post there. Or copy it there too, if @Franklin2 thinks that would help.

https://www.ford-trucks.com/forums/forum62/

 

In all of the tailgate window motor control circuit, there is only a single ground wire #57 BK that is connected to the dash tailgate window switch. This is the only negative voltage source in this entire circuit. Positive battery power is supplied to this circuit in two locations, #400 LB/BK at the dash switch in ACC or RUN and #517 BK/W to each of the rear Tailgate Window Switches. All of the other wires of the tailgate window circuit could be negative or positive voltage depending on the switch used and the position of this switch.

Now the Tailgate Latch Switch is a SPST switch that effects the tailgate motor no matter the requested motor action (up or down).
The method that I like to use on a DC circuit that could have current in ether direction is using a Digital Multi Meter to measure voltage drop. This article helps to explain it better than I ever could.
https://www.hagerty.com/articles-vid...g-voltage-drop
Using this method of measuring voltage drop, I've been able to measure the resistance of a connection, wire or switch. In your case I would connect my DMM across the Tailgate Latch Switch and attempt to operate the motor (for safety I substitute a tail light bulb for the motor). If the switch is open, the DMM will show the full battery voltage across it when a window switch is activated. This is because battery positive is present on one side and battery positive on the other side. If you do not see any voltage drop, or less than 0.2 VDC, the substitute motor (light bulb) should be on.
I've found that printing multiple copies of the above diagram and using different colored hi-lite markers to trace out the positive and negative wires in each of the 5 different circuit uses is a great visual aid.
Keep digging and you will find what is causing the issue.

 

Evan , the tailgate switch(key operated-on tailgate) is hot at all times ,using it up- down you should have power to motor .When the key is on (-Acc) position key in ignition-to - on, that the power for your switch in dash.
If correctly stated and you have power in the down position only , do you also have power on the key switch at tailgate???? (down only)if not there is other problems as this uses two different hot wires for the window circuit .The switches can be a pita ,dash switch and the tailgate switches can cause problems .IF THE MOTOR OPERATES IN EITHER DIRECTION YOUR SAFETY SWITCH IS NOT A PROBLEM
Bruner has provides the best schematic for the stock switch.
I can help you understand the schematic ,but you need to start from the dash switch first .TR

 

A sincere thank you to all of you for the helpful diagrams and suggestions! I'm a wiring newbie but I'm trying to learn as best I can.

I checked the dash switch - both up and down send power down the respective wires at the switch. Checked again at the wiring loom going into the tailgate. Again, the up and down wires from the dash switch were sending power. I did not check at the latch switch to see if power was getting to that plug from the dash switch.

I'm not sure how to take out the key switch and it's hard to get my test light in there and see what is getting power and what isn't. The black constant power wire is working, sending power to the key switch at all times, I probed it in the wire loom before it enters the tailgate.

What is confusing me is that I am only getting power to the safety switch in one direction of the key turn mechanism. If someone knows which direction to turn the key to put the window up and down and could share that information I could tell you all which circuit is getting power. I think the next try is to plug in the safety switch, latch the tailgate and see if the window will move - since I have confirmed power from the dash switch is getting to the tailgate.

One other thing: I see in the diagram that the dash switch runs through the key switch. If the key switch has gone bad, would that affect the signal from the dash switch getting to the motor?

 

Counter clock wise is up clock wise is down and yes if the switch is bad it will cause it not to operate with your dash switch,,have you disconnected your motor to see if it’s operable . TR