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Headlights coming on after car is switched off


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We had a 05 plate and had water ingress in passenger footwell. Body panels had not been sealed during Manufacture. BCM is normally on A post: relays, in fuse box under bonnet.

Ignition relay though may be inside under dash. 

I’m sure someone with a bit more knowledge than myself could pinpoint them.

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Just checked car for water ingress, can`t find any.  Changed headlight relay but problem still there.  Complete mystery.  Garage wants 150 pounds to check the car.  I am on a pension and can`t afford it at this time of year.  Many Thanks again all who are helping.  You are a great bunch here.

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11 minutes ago, Shivers said:

Thanks Starensis I will get an ignition relay tomorrow and try that solution. 

Do headlights come on even though headlamp switch is in off position? Are you sure it’s headlights coming on?

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The lighting is ecu controlled, do the lights stay on or do they turn them self on after the leaving the car - if you have auto lights it will have "Auto" on the stalk


First thing to do is get the Battery checked (Most places will do this FOC), the cold will reduce its capacity and or kill a weak Battery, if the voltage drops below a certain voltage it can make the electronics do weird things

If it's on its original Battery, it's at the end of its life, especially due to lock down, replace it with a Bosch s4/s5,Varta or Yuasa

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It can only be ECU/Module. Think column switch creates earth circuit to module, which in-turn activates headlamps from module. I'm sure someone will correct me if I'm wrong.

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Glad you got it fixed! Thanks for letting us know! :thumbsup:


On 12/12/2021 at 3:46 PM, flash22 said:

First thing to do is get the battery checked (Most places will do this FOC), the cold will reduce its capacity and or kill a weak battery, if the voltage drops below a certain voltage it can make the electronics do weird things

Can't believe you called this correctly! I would never have guessed a dying Battery could make the headlights turn *ON*!! :laugh: 


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Ah the wonders of modern technology, given the age of the car and OP's location, and the first of the very cold snaps


or it could just be Occam's razor

The principle gives precedence to simplicity: of two competing theories, the simpler explanation of an entity is to be preferred. The principle is also expressed as “Entities are not to be multiplied beyond necessity.”

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