Light controls and outside temperature reading.

[ChuckUK]

I know the issue of the auto lights not activating with no orange light on the mode selector has come up previously on this forum. This has been happening increasingly often for me, so I wondered if recent updates are a factor. Usually functionality is restored by turning the light selector control knob back and forth. However today I noticed an additional strange behaviour. The weather today was 21°C and sunny (quite unusual of late), but when I got in the car, which had been parked in the sun, the dash display read 8°C. I thought this would reset on restarting the car at the end of my journey, but I noticed that the light mode selector was also deactivated. When I twiddled the selector to bring it back to life the outside temperature rapidly increased to 20°C. It seems strange that the lights and the outside temperature are linked. Has anyone else observed this behaviour?

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[HuntingPudel]

I’m not sure what year your Mach-E is, but the headlight switch issue is related to the firmware in the headlight switch itself. The issue was corrected in late 2023, so the switch for a 2024 or later corrects the issue. The firmware in the switch itself is not addressable over the car’s communication bus, so a switch replacement is the only way to correct the issue. I replaced the switch on my 2021 (before I got my 2024) and I never saw the headlight bug show itself after the switch replacement. I put that same switch into my 2024 and have also never seen that issue in the 2024.

With regard to your outside air temperature reading, I cannot see how the headlight switch would have a bearing on it. My car occasionally reads high or low after being parked for a while but will generally read correctly after several minutes of driving.

 

[ChuckUK]

That’s good to know. So, it’s not something that is likely to get worse over time? If so what sort of cost would you expect for a new switch?

The temperature definitely felt related. The reading was persistently 8°C for a good 10 mins of driving when it usually reports high after being parked in the sun. It was the exact moment I rest the light switch that the temperature reading rapidly jumped up.

 

[Mach-Lee]

I know the issue of the auto lights not activating with no orange light on the mode selector has come up previously on this forum. This has been happening increasingly often for me, so I wondered if recent updates are a factor. Usually functionality is restored by turning the light selector control knob back and forth. However today I noticed an additional strange behaviour. The weather today was 21°C and sunny (quite unusual of late), but when I got in the car, which had been parked in the sun, the dash display read 8°C. I thought this would reset on restarting the car at the end of my journey, but I noticed that the light mode selector was also deactivated. When I twiddled the selector to bring it back to life the outside temperature rapidly increased to 20°C. It seems strange that the lights and the outside temperature are linked. Has anyone else observed this behaviour?

You have a bad headlight switch, replace it. It may drain your 12V battery. Faults can cascade to other modules if there is a glitch caused by it.

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