2010 Rear Defrost

[jman1200]

Winter is coming and with the first snow we've had I've noticed that the rear defrost is not melting the ice formed on the outside of the rear glass. Also, I do not see the warm lines clearing the fog on the inside.
Switch light turns on and it times out as it should.

I checked fuse 20 for continuity with a tester and it passed and swapped relay 56 with 55 (windshield wipers) and wipers worked after the swap.



I also found that cabin fuse 43 affects the defrost but also other stuff that is all working so this should not be the culprit.



Haven't checked the continuity on the glass element, not sure where the wires are but meanwhile, any suggestions?

 

[xFallenxCripplex]

Have you had the rear glass replaced? Rear end damage?i guess the solder is broken or unplugged.
Also remember the top portion is the radio antenna portion... Annoying when winter comes around.

Sent from my Pixel 4 XL using Tapatalk

 

[luigisho]

Check for continuity at the glass. Check the beginning of the power feed, then the end, then work toward the middle if you have to. If it is at the rear glass, there are conductive adhesives for tab reattachment and paint on condictive grid repair to get it working.

 

[jman1200]

Have you had the rear glass replaced? Rear end damage?i guess the solder is broken or unplugged.
Also remember the top portion is the radio antenna portion... Annoying when winter comes around.

I didn't buy it new but Carfax didn't report any rear end damage.

 

[jman1200]

Check for continuity at the glass. Check the beginning of the power feed, then the end, then work toward the middle if you have to. If it is at the rear glass, there are conductive adhesives for tab reattachment and paint on condictive grid repair to get it working.

That is what I plan to do next but haven't even look for the connectors, not sure where they are.
Isn't that grid covered in some sort of resin? Will you get a reading by touching it with a tester?

 

[luigisho]

Well I don't have the newer model cars but the concept is the same so there has to be a wire carrying power to the unit at the glass somewhere to transfer current to the grid on the glass. There may be some interior trim covering it but it has to be somewhere aroun the edges of the conductive grid

 

[SHOrod]

I

Isn't that grid covered in some sort of resin? Will you get a reading by touching it with a tester?

If you do not have window tint/film on your rear glass then they should be conductive all the way across. There is no insulating coating over the grid from the factory. I find that an old school test light is the best way to find breaks in the grids if they are too small for light to make it obvious. But in the case of the entire grid not working, that's going to be something more significant than a break in a grid line or two. You can use a test light or multimeter to determine if you are missing ground or power at the window.

-Rod

 

[Johnbigdog]

Feel/listen to the relaty when you turn on the defrost. If it clicks you know there is the input needed to activate the defrost. Now your chasing and output of the relay.

In the BJB pin 1 or 2 should have power on one pin. This is the coil of the relay and control side. The pin that doesn't have power should have ground when activated.

Pin 3 and 5 are the switch side. Again one pin should have power. One is the feed to the glass. If you want you can jump this with a jumper wire and a spade connectors.

If you remove the c pillar trim you will see the power and ground tabs on the glass. You can check available voltage at each tab to see if you read 12v when rear defrost is activated.

If you don't want to remove the trim, you can see if there is available voltage on the grid. DO NOT USE THE POINT OF YOUR METER LEADS. You will scratch of the grid lines and have to repair it. Take a piece of wire, strip off maybe a half inch of wire, fray it out and use that as your probe. It won't scratch the material off.

You can make two leads like that and volt drop the grid without removing the c pillar trim.

The rear glass also has an integral a.m. antenna. If you look at the top of the glass on the drivers side maybe within 6 inches down there should be a note of "antenna" and "defrost" or something like that.

 

[jman1200]

I know some of you haven't been able to sleep thinking about this....
So here's an update:

I was never able to find the issue and the rear window never got foggy except during Winter, so it didn't bother me.
For some reason I can't understand (remember that the definition of "insanity" is "trying the same thing over and over expecting a different result"), I kept pushing the defrost button every time I got in the car and there was ice on it, light came on but nothing happened. Well, this morning the darn thing started working, for the first time (that I recall) since I bought this car.
I guess the Gremlin in charge of jamming that system, passed.

 

[Bluezone]

I know some of you haven't been able to sleep thinking about this....
So here's an update:

I was never able to find the issue and the rear window never got foggy except during Winter, so it didn't bother me.
For some reason I can't understand (remember that the definition of "insanity" is "trying the same thing over and over expecting a different result"), I kept pushing the defrost button every time I got in the car and there was ice on it, light came on but nothing happened. Well, this morning the darn thing started working, for the first time (that I recall) since I bought this car.
I guess the Gremlin in charge of jamming that system, passed.

Perhaps you lost too much sleep and you imagined it.