2019 ford focus st line rear window deicer and wing mirrors not clearing . the button light comes on but the rear window and side mirrors aren't clearing from frost.

i've searched for a fuse but cannot locate one anywhere, help required please

Battery charge might be too low

Isn't it absolutely bonkers that accessories are shut off due to low SOC when the engine is running and power available from the alternator?

3 minutes ago, mjt said:

Isn't it absolutely bonkers that accessories are shut off due to low SOC when the engine is running and power available from the alternator?

The heated elements in the car can often pull more current than the alternator is designed to provide continuously. The battery acts like a buffer/reserve, so if it's low, they try to protect the battery and prioritise the systems that move the car and charge the battery enough for your next start.

That may be true of the front screen heater but I'd be surprised if it was for the rear screen and mirrors. Also this is a safety issue and the car shoud be designed to enable those accessories to function at all times.

On 1/15/2024 at 11:57 AM, INP1 said:

i've searched for a fuse but cannot locate one anywhere, help required please

Fuse F78 in the engine compartment.  [ called fuse F50 in some handbooks ]

On 1/15/2024 at 11:57 AM, INP1 said:

i've searched for a fuse but cannot locate one anywhere, help required please

So have you found it yet ? 🤔

Sorry been away, it's started working again so have just carried on regardless, maybe the battery low state of charge theory kicked in