2007 Navigator - Rear hatch mostly dead

[BigCarBigFamily]

Hi, new to the forum, just recently picked up a new to me 2007 Navigator in overall pretty good condition but the back hatch is vexing and I have extremely limited electrical troubleshooting knowledge.

Here's a breakdown:
- The control panel shows a "liftgate/liftgate glass open" message.
- Neither the liftgate nor liftgate glass controls work to open the latches (controls on hatch, on keys or up front), the power liftgate functionality is disabled in the settings and the motor on that is probably burnt out, not a big deal to me.
- I do hear an electric clicking sound up front when I press the liftgate glass button or pull the liftgate hatch handle.
- The Windshield wiper doesn't work at all either, I think it was totally fried - the fuse for it was missing in the box and the shaft was frozen solid with a white powder corrosion, I had to cut the nut off the windshield wiper shaft on the glass to get it removed.
- The lower hatch brake lights and license plate lights don't work (tried new bulbs).
- The high mount brake light does work just fine - interesting note, it stopped working when the liftgate glass motor was unhooked.
- I went ahead and replaced the windshield wiper motor, liftgate glass latch, and liftgate latch - no real changes but I am sure they would work now if they were getting power properly.
- All fuses have been checked, 2x or more at this point. I also have pulled the battery cables for more than 20 seconds once and the main liftgate fuse a few times to see if that would do anything. Really, all fuses related to the hatch have been pulled to see if that does anything.

Any ideas? Also, slightly related, is there anyway to force the liftgate window latch to pop open? My replacement arrived closed and with no power or anything I can't even get it open to stick the latch in and see if that affects anything.

 

[BigCarBigFamily]

I am approaching the end of what I can think of to troubleshoot this.

I got a wiring diagram book and noted that everything impacted seemed to run through grounds 400 and 401 under left rear window and I was able to get to them, which requires removing a liftgate control module that blocks access them and they read good on with my multimeter. Voltage coming off the engine is 14.6, voltage at the grounds is 14.5 so well within expected parameters.

There is a voltage drop at the hatch itself in that everything that I could easily measure except for the high mount brake light, was showing ~11.3 volts. The module looks fine and clean, when I take cables out of it and plug them back in it does seem to cycle something on the locks on the hatch itself, interestingly if I remove that liftgate control module the voltage at the non-working tail and license plate lights bumps up to 13.7, which still seems low, but much closer to what they should be and the lights still don't work.

Should I be replacing that liftgate control module or is that voltage drop normal.

 

[KOTU]

Wow, what a mystery. It sounds as though you have done a lot of good troubleshooting. My thought would be to inspect all the wiring for breaks in the insulation. Given that you have a wiring diagram, check that color-coded wires go to and from the correct place. Was a different configuration of an after-market wire harness installed for towing? Maybe this is when wires were crossed or spiced into. The white powder corrosion seems suspect for electrolysis occurring, the wiper motor may have been replaced in the past and had been wired wrong when the replacement was installed. Is it the right motor?... I also have a 2007 Lincoln Navigator L

 

[BigCarBigFamily]

Thanks for the suggestions - The wiring is pristine, you wouldn't have any idea how old this car was if just from what was under the trim.
It has a factory tow package, there are no splices or other work I can find any trace of in the wiring harness, it looks factory new still wrapped and untouched. All the colors I can see match up to where they are supposed to be going per the diagram. The wiper motor appears to have been the factory one.

I have gotten forscan lite and run a full reset on the liftgate module with no change in behavior. I got a used module as well and it shows the exact same symptoms so that kind of rules out the module as the root cause in my mind.

Testing the module in forscan shows

 

[BigCarBigFamily]

I have to take my licks here - when I was doing all my checking up to this point I largely neglected a failure point, which is where the rear wiring harness connects before entering the hatch. I had merely glanced in with a light without pulling down the trim or headliner and it "looked fine" to me.

Well, today because I was considering pulling and replacing the whole harness I pulled everything down and half the wiring harness was disconnected. I could only speculate as to why someone would have ever done this, left it that way and sealed it back up, and it was obviously intentional as that connector isn't coming apart on its own.

After fixing that most everything in back works just fine now - lights, rear window release, latch handle even the actual power liftgate function all work.

I am left with one single issue which is it still thinks the liftglass is open - this doesn't prevent the window release from working but it keeps the interior lights on always (unless turned off entirely up front) and keeps the rear wiper from running. This one baffles me a bit unless that new latch I got has a fault switch but it's a huge improvement.

 

[KOTU]

I'm happy you found your solution. How's this for a cause of the wiring being disconnected? At some point in your Navigator's past, the sliding mechanism on/in the sunroof was replaced. To do this work, the headliner has to be removed. I clue into this because I plan to do the same work. My sunroof motor works but it doesn't slide, so, I'm going to replace the sliding mechanism on/in the sunroof. Knowing a wiring harness is there is a good heads-up, thank you. I've been dreading having to remove the headliner. Next week I plan to do it. Any tips you can give me would be appreciated.
Two years ago, I had that click-click-click from the engine I tore the engine apart and replaced all the timing components, roller rockers, lifters, water pump, oil pump, fan clutch. I took pictures and followed the directions from the FordTechMakuloco YouTube channel