Feathermerchant

The circuit powering the defrost grids is switched + not switched ground. You should see 12V at the yellow wire when the system is on. I think you found that you were getting voltage on the yellow wire. If you read 617 Ohms from the spade where the yellow wire goes to ground, then at 12V that's only about 12 / 617 = 0.02 Amps. To get a 10A load the resistance needs to be about 1.2 Ohms. So you still have a high resistance. See if you can measure each grid separately. It will require an Ohmmeter that can measure less than 1 Ohm.
If you can't do that, read the voltage drop across each of the three grids with the system on. My guess is that two read 0 and one will read about 12V. That will be the one with the problem.

rbailey3711

Hi Feathermerchant,

BTW, my name is Rick.

The control circuit is the switched ground from the HVAC modules. You are right that through the contacts of Relay #4, it is a 12V signal. According to the wiring diagram, the resistor is in the grid circuit and connects back to the HVAC Status section of the HVAC Module.

When you press the switch on the HVAC module, energizing and de-energizing the relay, the battery voltage is on and off on my voltmeter. And, the mirror circuit works so the 12V is there for connection 56-3.

I'll do the resistance checks you've suggested. There isn't a open/closed limit switch that isn't shown on the schematic is there? Not the two high current switches which are the two switches on the slider...I think.

Thanks, Rick

Feathermerchant

Yes I think the only switches are on the window. I think you'll have to measure voltage instead of resistance.

rbailey3711

Hi,
The only coil that had continuity was the slider. Not sure how coils went unless its right at the spade lug connections, no scratches through any of the grid lines.
Ford says there are no TSBs or recalls for the rear window defroster circuits, even though my dealership has seen a few of these come in.
I was hoping Ford Customer Service was following this thread and might have some ideas. If it was a new issue, I'd say shame on me for buying another White Ford. Only white vehicles I've had since 1979, I've had issues. '95 Exploder, trans went out at 1800 miles. 2013, motor went at 19486.3 miles [warranty replacement], right rear shock blew out at 39487 miles and now rear window defroster at 43236 miles. Shock & window aren't covered under my power train warranty.
Oh well, live and learn!!!!

Feathermerchant

So BOTH of the fixed window grids are out? That surprises me.
If you are determined, you can fix them. Measure resistance from a spade to the grid midpoint. That will narrow down where the trouble is. Then in the trouble area, measure from one end to the trouble area midpoint. Each time you will cut the possible failure area in half.
I agree you should check the area near the spades. You can get grid repair kits.

jfdid

Folks, I dug into mine yesterday. 2011 F150 Supercrew. See attached pics.


I pulled the window out to troubleshoot and find the connection between the passenger side spade connector and the slider contact.


Note: grids should read about 0.5 Ohms. My slider read 0.4 Ohms, my driver's window read 0.5 Ohms but the passenger read 80 Ohms. This turned out to be a connection problem between the negative side of the grid(meaning the part closest to the middle of the truck) and the contact at the slider. The wire/conductor is part of the lamination of the window and travels below or above the slider window over to the contact. This is integral to the window and is unserviceable - trust me, we dug pretty deep into it.


So the problem isn't with the grids themselves or the contact assembly, but with the connection within the window.


For the record, the slider contacts are physical contacts(not induction coils etc). I'd be surprised if these caused an issue for most people. Another note: They are NOT removable. They are soldered onto the window - I broke the solder when I pried them off. See picture of contact assembly. The plastic cover doesn't look like it comes off either, so probably don't do much prying on this at all.


The way this whole system should work:
Push defrost button on HVAC controls. HVAC module grounds BN-BU wire and activates relay. Relay switches 12V power to the back window(BN-YE). The 12V goes into the spade connector on the passenger side of the window, through the heater grid on the passenger window. It then travels via a conductor within the window itself over to the TOP contact on the slider contact assembly. When the slider is closed, the current travels through the contact, through the center window grid and back through the contact. Current then flows through the driver grid and out the spade connector on the driver's side, through a wire and to frame ground. Some signal voltage is then fed back to the HVAC module to tell it that the defrost is on and working. This is the skinny yellow wire on my 2011. By the looks of the schematic, there may be a resistor in-line with this wire so I'm not sure if it's actually a 12V signal or less than that.


Regardless, if your defrost isn't working and you want it fixed, you're likely going to need a new window. They're pretty easy to take out and put back in if you're a DIY guy.


If you're not going to fix the defrost and you just want the LED on the button to work to indicate your heated mirrors are on, then you can just wire the 12V back to the signal wire(I'd try with a resistor first in case the full 12V fries the LED try here: http://www.instructables.com/id/Choo...Use-With-LEDs/).


Any questions, let me know guys.

Feathermerchant

Great write up. The plastic cover should be able to be removed from the contacts. I'd guess the contacts are soldered on first then the cover is installed. Could you fix the problem by soldering a wire to the end of the pass grid then to the contact? Or are the grids buried in the window?

rbailey3711

jfdid,
As Feathermerchant said, great write up.
Yes, that bulge in the yellow wire is a resistor; I read 338 ohms but, I don't know if that is the correct resistance.
I find your 80 ohm reading to be interesting, I read in the mega-ohms between the two connections and the high current switches on the window and not the slider. On the slider, I read continuity [zero ohms].
I have been in contact with Ford Customer Care and they may do something, even though I'm out of warranty. I'm supposed to bring the truck into the dealer on Monday. I think I will look for the ground connection and do some more troubleshooting this weekend. Everything I was measuring was between the two spade lugs on the passenger side.
Also, I was able to get the plastic cover off without breaking the switches off of the slider. If your window is still serviceable, you can get liquid solder and put the switches back on the slider. They did use some kinds of silicone sealer to glue the cover on the switches.
I still think Ford should do something since this isn't a year specific issue. I will let you all know after Monday.
Have a Happy Thanksgiving.

Ynot4me2

Wow, as the guys said, nice work and write up JFDID. Just an FYI, I was able to remove and put back the cover on the slider simply by pushing upwards on it to remove it on my 2010.


"The wire/conductor is part of the lamination of the window and travels below or above the slider window over to the contact. This is integral to the window and is unserviceable" That's what I suspected was the problem and found no way to fix it.


Now, I'd be really interested in a write up on getting my LED back without the rear defroster. If you look at my pic in post #28, I've got 3 wires, which ones and how would I connect?


Maybe also a write up on replacing the rear window although that window is $$$. I've never done that but there's always a first time.


God I love this forum. So much info and advise.


rbailey3711, I agree 100% Ford should be doing something about it.

rbailey3711

Hi Ynot4me2,
Your 2010 may have the ground in the same connector and that may be why you have the three wires. The newer ones we have in these pictures have the ground separate, based on the diagram [I haven't located the ground, yet].
If you have a resistor in the white wire, you may be able to put [jumper in, with it disconnected from the window at the connector with your three wires] 12V feeding back to the HVAC module to see if the LED lights. I'd really like to find a schematic of the HVAC module before I'm sure what is in it. On the newer units, it is a switched signal that gets a voltage drop and current through the yellow wire back to the Status section of the HVAC module, jfdid had it marked on his copy of the schematic. It comes off the driver's side grid in his diagrams. Do you have the schematics for your 2010? If you do and can post them, we may be able to make a more educated guess at what the three wires are for in your harness.
Happy Black Friday,
rbailey3711