I don’t believe my heated screen is working properly, 2017 ST Line. When defrosting it the last couple of mornings I turn it on and the light illuminates but the screen doesn’t seem to clear properly. It takes about 5 minutes to clear and seems to defrost from the bottom up, with the patterns of the screen blowers visible as the shape of the area defrosting. Is there an easy way I can check if the screen is functioning when it is not frozen? Can I put a multimeter on it anywhere? I know it works in two halves and both halves seem to work the same as each other. My Mondeo and the wife’s mk7.5 fiesta worked much better.

Also, when using the blowers at full temp and fan speed on 4 there is a marked difference in the speed when pulling away and when coming off the accelerator. It will speed up and run at what I would expect 4 to sound and feel like but when you back off the throttle or idle the fans seem to slow right down. I’ve never experienced this before, could the battery be a duff one? 

 

Thanks in advance for any responses.

The blower speed is normal, I'm not sure if it's to reduce engine load at a standstill or if it's done for comfort and reduced cabin noise but that's nothing to worry about.

As for the screen, are you trying to melt ice under snow as they don't seem to like that, quicker to just wipe the snow off first.  Takes literally 30 seconds to melt a screen of ice on my mk3 though so 5 minutes sounds wrong.   Should defrost in vertical bars and leave 2 thick lines by the A pillars if it's defrosting properly.

 

It sounds as if your screen is working ok as the effects you describe are due to the very high current it takes. I've noticed wipers slowing down etc. when the screen is on. Since your car is only 1 year old (or possibly less) it's unlikely to be your battery, although it's not impossible for a battery to fail early. The alternator can't provide enough current at idle to balance the load of the screen and all the other auxiliaries plus charge the battery so the voltage will inevitably drop.

 

Thanks Tom, that’s reassured me about the blowers. I’m just not to used to hearing that happen, but if it’s normal then I’m good with that. Regarding the screen, what you have described and what the pictures show are what used to happen on my Mondeo and what does still happen on my wife’s my Fiesta so something is very wrong and I will take it back to get looked at. 

 

Hi Mike, I think I may have misled you a little. The difference in fan speeds etc was all done while the screen was off so it was not drawing anything from the battery. I have noticed the windows can go very slow at times too. The Mondeo battery is known to be quite poor and often does not last very long for one reason or another so that is my reasoning when askin about the focus battery. The battery on the focus must be more reliable. 

Ill report back with the garages findings, thanks guys.