Why is my Ford S max heated windscreen not working?

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Nick B. February 8, 2021
There are two main reasons why the Ford S Max's heated windshield will fail to work -- most notably, one of two different fuses may blow, or the heated windscreen itself will fail. The first thing that You should check are the two relevant fuses, since they'll save You quite a bit of money. However, fuse failure is usually indicative of a larger wiring issue, since they're there to act as failsafes -- if they blow more than once, You should look elsewhere in the system. Particularly, You'll be looking for Ford 40A cartridge fuses within the fuse panel. Luckily, these can be found quite inexpensively, either alone or in a multipack, so You can likely have some extra to keep on hand. The total cost of the repair, if it happens to be the fuses, should come in under ten dollars.
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Jack Black December 14, 2022
It turns out that there is a more usual cause here, as per several forum threads all over the web. The Battery Management System will not start the heating panel if it thinks the battery is too old or the charge level is too low. The cause of this is that battery charging rate has been reduced after a recall due to environment protection purposes (to lower emission). The car in general does not bother but the front screen heating and sometimes start/stop module are prevented from igniting by the BMS. Solutions: 1. Try resetting the BMS: you can find two or three methods that don't require PC, just pushing buttons and pedals (not a joke!). After, even if the BMS sees the same charge% as before (like 64%), it will start the heater panel. (This sometimes also solves the non-operational Stop/start.) 2. Try travelling a longer journey (more than 2 hours), which gives enough time for the car to fully recharge the battery.
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Jeffrey M July 30, 2020
If your Ford S Max heated windscreen is not working you will want to check the wiring to it.
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