Well, it's a 3 wire switch, "Liftgate fork" sure sounds like a latch to me. And he did see a 3-wire plug on his latch so... Anyway, I don't think the switch is bad. Only way to know for sure is to measure it with a multimeter using the diagram above to see if it makes contact as it should. But the liftgate operates normally, opens and closes as it should Without that switch, I'm pretty sure the module would lose its important signal which tells it that the liftgate is locked and thus throw a code or at least disable the liftgate. Correct me if I'm wrong, but that's how it looks on the diagram at least. I'll have to read the service and pinpoint test section in the workshop manual to see for sure, but oh well.. Not meaning to **** anyone off here.

 

You're not, the design is. BTW, the wire colors and circuit numbers for the switch you pointed out don't match the wires going to the ajar switch. I'm just sayin'.

 

Because they're connected to the power liftgate module. The power liftgate module is connected from pin 10 to the wire where the rear glass ajar switch is connected. It's not an easy diagram to follow when it jumps between so many different pages, but I'm an automation engineer by profession so I've spent my fair share of time reading diagrams on bigger systems, though their style is a bit different than the automotive wiring diagrams..

 

This is how it is connected together. The reference to power liftgate matches the VSM wire going from pin 10 on the power liftgate. I assume the power liftgate module has a internal relay or solid state output which acts as the actual ajar switch in place of the traditional ajar switch from the manual liftgate. Then the liftgate module most likely determines if the power liftgate is closed based on inputs from the fork switch. Though it may use a combination of sensor inputs, who knows. The reason the liftgate ajar message never goes away is because the liftgate never gives the signal to the VSM, if this is due to a broken wire, internal fault in that output in the liftgate module or some input lacking from the liftgate, I don't know, and you need a scanner to read the inputs and outputs to see what goes on, such as the FORScan (free) or a Ford VCM (expensive). Since the power liftgate still works, I guess it sees the inputs from the sensors and switches in the liftgate. If it looses those, I'm sure it will quickly disable the liftgate to prevent damage.

 

I guess a dirty way of fixing it would be to just ground pin 12 on the VSM connector, or run a wire from pin 1 on the rear glass connector (C4040) to pin 12 on the VSM (C2113a). That would permanently disable the ajar input from the liftgate module, though it might be interesting to actually diagnose it and find out where the fault actually is. It may be tempting to suspect the switch, but since the switch is not directly communicating the ajar signal, while the module is the one who actually gives that output, it may be more likely that the problem is at the module. Still, hard to know without a scanner.

 

Does anyone know if the "liftgate ajar" message means the liftgate itself, or is the same message displayed if it's the rear glass that is ajar?

 

On the Expedition it's one message for both. It says "LIFTGATE OR GLASS AJAR" or something along those lines. Not sure if it's different on the Navigator, and as far as the diagram shows, the switches for both liftgate and rear glass seems to open the same circuit. Open circuit means one of them are open, closed circuit (pin 12 on VSM connector C2113a is grounded) means both are closed.

I think the only difference on the "ajar" messages in the Navigator from the Expedition is that the Expy only says "Door ajar", while the Navigator tells you which door. At least I think I read somewhere that the Navigator shows which door.

 

While they can be the same circuit, they cannot be the same switch. So another possibility is the dome light is on because of the glass ajar switch.

 

It could be either the liftgate switch or the glass switch yes, those two switches are connected in series. That's a possibility we havent thought of before actually. Its a while since the OP has posted, but hopefully he can check tge ajar switch in the rear glass. Its more likely that one which is the cause of the problem, since the power liftgate still works normally.

 

The ajar switch won't stop the liftgate from working. If it did the motors would stop the moment the ajar switch tripped. The glass ajar switch will stop the rear wiper from working, so there's a possible test to help narrow the issue down.

 

What I mean is that the fork switches in the liftgate latch itself would probably disable the liftgate from operating if they gave conflicting signals, i.e. other sensors show liftgate as closed, the module has commanded it to close and still reads it as unlatched, it would probably freak out and stop working.

Since it works, I suspect the switches in the liftgate itself works fine, but that the problem either lies with the output from the liftgate module (which is in series with the rear glass ajar switch) or with the ajar switch on the rear glass are not working. Or the circuit is broken somewhere. And I wouldn't be surprised if a can of WD40 on the rear glass latch and working it a bit would fix the issue. He only tried that on the liftgate latch I guess, and not on the rear glass latch.

 

I'd sure be pissed if I replaced the latch for $300 and it turned out that a blast from a can of WD-40 would have fixed it.

 

Exactly. That's why proper diagnosis and confirming the issue is important, instead of assuming things and throwing parts at it. I hope the OP is still around to give feedback on the issue.

 

We didn't really give him much of a chance to add anything.

 

Sorry guys, it stopped raining so I was able to experiment on the switch, etc.

FYI: At least on my Navigator you need to reset the computer after every test or it continues to read "liftgate or rear glass ajar" even if it is fixed.

That was a frustrating learning experience.

Meanwhile I did just about everything possible before finding that out, so I just don't know what fixed it. Cleaned it with wd40 and then contact cleaner when the wd40 didn't work. Checked all the contacts. Shorted some wires. Removed some wires. Replugged things back in. Tested the switches dozens of times. Nothing I did had any affect at all. Which just didn't seem right. Something should have had at least an intermittent affect.

So, I decided to cut disconnect the battery overnight to reset the computer in case the computer was retaining the message and not clearing it when I messed around with things. It worked. And, unfortunately I have absolutely no idea which of the things I did fixed it. Or, maybe it was the computer was just wacked out.

Even my dimmer switch turned out the dome lights after the reset. I know it isn't pc, but I think my trucks brain is mental.
Thanks for the help!
I need a few beers.