I have a strange fault. My heated windscreen does not work in heavy frost. I have taken it to the dealer who has tested it and assures me it is working but the next heavy frost it doesn’t clear. Anyone else had this fault

It's not a fault - It's a feature !

The heated front screen takes a huge amount of power to operate, up to 4 times more than the rear screen. It will only operate if it cold enough, and if the battery state of charge is better than 70% and that the engine is running.

Charge your car battery overnight and chances are it will work (provided its cold).

The default charging system only allows up to 80% battery charge and the alternator does not deliver its full potential current. This is all in the name of emissions as the alternator creates a slight drag when charging. Charging your car overnight can help, but that is a ridiculous thing to have to do. You can use FORSCAN to change the state of charge target to a higher number. I have changed mine to 90% and the stop/start and heated screen now work when needed.

 

I just signed up here after recently purchasing a 2016 smax. Unfortunately I didn't confirm the heated screen was working as it's not really been required until now. I've done a few bits of testing of fuses and with forscan but the battery charge level sounds like it could be the one.

Just out of interest is there some way of seeing current battery charge level in forscan or in the car menus somewhere? Same question for battery last replaced timer.

Thanks

 

 

Hello Spencer, I would be very surprised if there is a fault with your heated front screen. Simply charge the battery for 12 hours, wait for the temperature to fall to less than 7C, start engine and switch on the screen 😀

Get yourself a decent multimeter and measure the voltage at the battery terminals 30 minutes after parking. Then you will be able to get the correct state of charge reading.

 

 

 

 

You can see the current SOC with Forscan, you can set up various values to be displayed. You set it up with the Read PID icon, the 3rd one down on the left, then double-click on a box to add a gauge.

Got it, thanks.

To confirm, upped the charge state target to 90 and the screen started working immediately so thanks for the tip.

Battery charge was 63% so hopefully now this should now start to increase also.

I have a 2017 SMAX, it's heated windscreen has never worked since owning!! Ford never diagnosed it properly, just said I wasn't driving it farr enough. Ford recharged my battery and it worked....if they left the jump leads on when starting... so "there is no fault Sir!" 

The recharged battery at 100% SOC retained only 55% after it's first start with no jump/charging leads left on, so the heated windscreen does not work as the SOC read by the car is less than 75%!!!! Ford would not replace the battery as it retains >50% SOC after repeated starts! So new battery should fix it? Not quite, Ford tried that and after 1 start, same detail! Heated windscreen fails to function.

I think at 4 years old now, only discovering the SOC target can be changed might mean I can find someone to update my car to see of finally, we can have the £400 option functioning as my superb 2016 Skoda Superb's did evey time without fail! Same journeys & mileage! 

Thanks for the knowledge the SOC can be amended. This is New Year's resolution #1, get SOC target changed & a new battery!!

Changing the SOC to 90% was the best thing I did with my S-Max. Everything works when I want it to , not when the car decides. My previous car was a Skoda Octavia and the heated screen worked all the time in all conditions. Good luck with the change. It is very easy to do yourself if you cannot find someone near to you with a lead.

 

9 hours ago, blahde2 said:

This is New Year's resolution #1, get SOC target changed & a new battery!!

If you find yourself in the North East of England, I will be happy to adjust it for you. Best to set SOC for 90 or 95%, it kind of depends on if you do lots of short journeys.

 

I had exactly the same issue along with Auto start Stop. Took it to main dealer who said battery is not charged enough.  They charged it but was unable to test it until today (-1C) Did not heat up!  (Note that I charged the battery the day before to prove one way or another.)  I will try this Forscan tip.  Oddly for Ford, my 2013 SMax that I part exed in never had any issues with heated screen.

On 11/30/2021 at 10:48 PM, unofix said:

It's not a fault - It's a feature !

The heated front screen takes a huge amount of power to operate, up to 4 times more than the rear screen. It will only operate if it cold enough, and if the battery state of charge is better than 70% and that the engine is running.

Charge your car battery overnight and chances are it will work (provided its cold).

Wow, is that right? I never knew that, You learn something new everyday!