Does anyone have a good testing procedure to diagnose what the issue could be?

I checked the F15 30A fuse, looks good. Not sure how to test the relay, or frankly where it is, as I can't find a picture/diagram anywhere for it. R3 I believe

I'm hoping it is just a relay and I can swap it for another on the car to test.

Its a 2013 VIN..44671 XKL Portfolio 3.0

 

Ken, if you pull down the center console in the rear seat, you will notice that there is loose fabric there. You should be able to pull the fabric out of the way and this is going to expose a fuse box. This is going to have fuse F15 and relay R3 in it. If you look at the fuse, you will see 2 silver tabs in the top. You can use a multimeter and check for 12 VDC on each of these tabs (red lead touching one of the metal tabs, the black lead on any part of the body). If you get 12 VDC only on 1 of the tabs, then the fuse is bad. Next, locate the relay. PUll it out and you should see 5 terminals inside of the opening and they should be labeled 1 thru 5. If you stick your multimeter between pin 2 and chassis ground while measuring resistance, you should see it drop to a low resistance (under 10 ohms) when the defroster is turned on. If not, then you have a bad control module. If you jumper then between spots 3 and 4, after a minute or two, you should start to feel the rear window get warm. That would indicate that the heater is working and therefore you problem is relay R3. if the heater is not getting warm at this time, you either have a bad RF module or the heater is broken. You would then have to measure for 12 VDC on the metal tabs on the rear window and see if you have 12 VDC on one tabe and 0 VDC on the other. If you have the same voltage on both sides, if 12 VDC, you have a bad ground wire between the glass and the body of the car. If you have 0 VDC, you have a wiring problem between the fuse box and the window or the RF module is toast.

 

Hi,

Thank you very much, what is the " RF module", and where is it located?

 

The RF module is a noise blocker. It shunts the RF signal that can be generated from the antenna being in the window from getting into the electrical system and introducing what most would think of as "alternator noise". The filter is located in the rear C pillar (behind the cloth panel on the left side when sitting on the seat, looking at the rear of the car. (so, your passenger rear corner on the C pillar, inside the car). Should be easy to find as you can trace the wiring from the window there and you should only have but a few inches/centimeters of wire before seeing a "black box" which would be the RF module.

 

Great diagnostic instructions from Thermo. But I can't find the relay in one of the Jaguar Parts locators. Is it a 5 pin 40 Amp relay like C2Z2978 .
Is there a pic of where the relay is located in the rear seat fuse box?
Does that same relay also control the door mounted rear view mirror heat?
On my 2016 XJL, no rear window defrost, and no heated mirrors.
I would appreciate any suggestions.