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Had an issue with my heated front screen for a year now. Dealer wants 850 to correct this but won't tell me the issue. My guess is they don't know and want to change everything. Basically it won't work. Fuses are ok but the switch won't light up. Have changed switch still the same. Any clues please
Sorry - here's the test procedure you can do at home for the MFU.
Pix of internal as well. It is a small box on the back of the fuse panel, times lots of things in the truck, and is not really something to tinker with unless you like component level printed circuit board repair. Not a well designed unit, I replaced one because it had melted a hole in the case by overheating. Change out interior dome lights and cargo light bulbs to LED to improve life of the MFU (reduces power that must be "dimmed").
The MFU can die on just a single function, or more than one. The file I attached is the RAVE method of starting a demo test cycle that runs thru them all, so you can verify the module is operating things. No hand tools required, just hands.
Pressing the switch requests the MFU to engage the relay, which powers up the front screen elements and lights the button. So if pushing button does not make a click, it would be relay or MAF. And without turning yourself into a pretzel the above posted test diagnostic will test the MFU. When you have to replace it, you will find the reason it is called the MF U. Suggest you disconnect battery when trying to move the fuse block around....
I replaced my MFU chasing the dome lights, and the rear wiper started working (it was way down the list). It is replaced in the D2 with the more complex BCU.
Heated front windscreen
