rbailey3711

White Platinum, the relay does not have a holding circuit, it has a back diode to protect the battery/source against current surges.

Haven't found anything else on the rear window defroster resistance. I do know the reading changes when the slider is opened or closed. Still trying to figure out where it is getting lost from the heater control switch. Also haven't had any feedback on how to tell that the heater is working if the switch isn't lighting on the dash/heater control. Mine is definitely not working!!

ef1Fiddy

Hi Guys,

Was just reading this page this morning and I think I know what's going on....

Just picked up my '13 Lariat Screw last Saturday. Going to see if the dealership (non Ford) will fix it (GoAuto group). Read what everyone has been saying about the rear window being closed with contact points but I think you're looking at the wrong ones.

If you look at the slider, there is a small black rectangle bar on the right side. I think what happens is when it closes, there are 2-3 contacts that touch the element on the glass, making contact for the defroster itself. The foam padding on mine looked a little torn so I'm not sure if it was worked on in the past but most likely the culprit.

You might be able to use a non metal scraper to remove the cover and check the contacts. Can't find a good picture online, I'm heading for coffee and will take a picture myself and post soon after.

ef1Fiddy

This piece:




Contact points:





Still waiting to hear back from my sales guy (actually one of my good buddies before he got into car sales, still is, 3 vehicles in the last year lol)

rbailey3711

Those contacts need to be closed to get continuity for the defogger and the heated mirrors. Those are the magnetic switches [Hall Effect] talked about earlier in this thread.
In the previous post, picture of blue connector [on the '13 its gray & only two wires], if you unplug there and use an ohmmeter I read 338 ohms with the window closed and 7.82M ohms with the slider open.
Not sure where to check now!!!

ef1Fiddy

Ahhh sorry, I was thinking there were physical contacts and thought that there were other points for the magnetic connections etc. Makes sense to use magnets as there would be no contact wear, but interesting if they are losing their

The dealership is going to take a look at it today, better fix it at no cost (long story) and I'll report back what they find or replace.

Feathermerchant

According to this wiring diagram, the switches are contacts on the slider (I believe). If they are open, there is no rear window heat but the mirrors should heat. Also the indicator light will not be illuminated. If nothing is heating then check the voltage at the window connector. If it is 0 then check the relay and fuse.

Ynot4me2

Hi guys, if you push up on that casing (on the slider) the cover will come off. I know I've done it on mine while trying to troubleshoot why my rear defroster no longer works (BTW, the light on the dash switch no longer comes on but my mirror defroster works). Once the cover is off you'll that they in fact are physical pressure contacts and not magnetic. I've tried cleaning mine and re seating them but to no success. Still does not come on. On the other threads, it seems like a defect in the rear window and the only fix is to replace it (entire rear window). I've spent a bit of time trying and looking for a fix without success. I suspect that it has something to do with the 2 smaller wires going into the window by the tab on the passenger side. At least on my 2010 SCREW (see pics on #28).


Keep us updated if you find something.

rbailey3711

Looking at the schematic Feathermerchant provided, the "Call for Heat" is a switched ground signal from the HVAC module. That provides the ground to the relay coil. It appears, by this diagram that the mirrors should work if the relay is working, independent of the rear window defroster, if the switched ground is getting to the relay. The only portion that won't be working is the status light (amber light next to switch on dash). Somewhere in the system there has to be a holding circuit to keep the relay energized. It is also a timer circuit so that the relay de-energizes based on current, heat or time. I'm assuming that is part of the HVAC module and its internals aren't shown on this diagram. I'll do some more checks and let y'all know what I find.

BTW, I did do some more searching on the forums and this is not a new issue for the power rear sliders with defrosters. The oldest post I found was for a 2010 F150 and it has been presented to FORD and it doesn't have a TSB or recall, according to my dealership service department.

Feathermerchant

That box with "Defrost Request" has the control circuitry in it.

rbailey3711

Thanks for your schematic page Feathermerchant.
I did some more checking; even though the light doesn't light on the dash, the mirror circuit works and I have battery voltage at the connector on the passenger side to the rear defroster. I did get the cover off of the window switches [high current switch] in the schematic. They were dirty so I cleaned them. I get a continuity reading across each switch with the window closed. I hooked up my ammeter in the circuit and had no current flowing through the rear window defroster. I know I said earlier I was getting 338 ohms for the window coils; I unplugged the yellow wire from the spade lug and then read 617 ohms at the spade lugs....not sure why I got the difference like that because in the yellow wire is an inline resistor for current limiting.
Before I forget about the dash switch, the control circuit does work and it will turn on and off the voltage [switched ground] when you press the switch. I used a stopwatch to test the timer and it did not turn off automatically after 10 minutes like the owners manual states. Mine ran 14 minutes before I decided to shut it off.
I also sent another email to my dealership after reading a bunch more posts on this same issue and found that Ford did have a TSP back in 2010.
Anyone ready for a class action suit? I'd sure like to talk to the engineer that designed this circuitry.
I haven't given up and I'll continue to troubleshoot the circuitry. The schematic drawing for the rear window grid doesn't make sense electrically. It is a switched ground from the HVAC module yet the diagram shows a set of coils going straight to ground. To me, once Relay #4 closes the contacts and the slider is closed, there should be current flowing through the grid.