Exterior Lights coming on and off

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Conorc1983

New Member
Joined
Dec 27, 2022
Messages
17
Location
Northern Ireland
Car
C220 cdi 2006
Hi all - wondering if i can ask some advice as searching doesn't seem to bring up my issue.

The w203 C220 cdi that i had purchased a few weeks ago now has a working front engine cooling fan and working coolant level sensor thanks to you lovely people. Another weird issue has cropped up that i need some assistance with.

When the car is locked, no matter which position the light switch is in, the front and rear lights illuminate randomly all through the night. I just caught this last night as i was going to bed. When i looked at the camera, they come on and off at least 20 times in an hour. Obviously this is draining the battery so I've left it on a trickle charge.

As some troubleshooting, I've checked fuses 50 & 63 for light modules and they seem fine. I had also disconnected the light switch itself to eliminate the fact that could be at fault. The previous owner had said it needed a new alternator, but surely a faulty alternator couldn't cause such an issue? Could it?

Any help and assistance that you could provide would be greatly appreciated as the mechanic that i was going to bring it to has been downed with covid for a few days.
 
I have no idea if its the same fault....but I had a very similar issue with my C209.....disconnecting the battery overnight cured it and it never came back.
 
I had a 'similar' issue on a 203.
That was water ingress at the screen, allowing water on to the light switch by the ignition. It was confusing the SAM.

Could be water getting to any part of the switches.
Could be the SAM itself.
 
I had a 'similar' issue on a 203.
That was water ingress at the screen, allowing water on to the light switch by the ignition. It was confusing the SAM.

Could be water getting to any part of the switches.
Could be the SAM itself.
Funny I actually had the fuse cover off for a few days while I was troubleshooting issues with the coolant level sensor! Should I bring it into the garage and maybe get a hairdryer into the SAM area?
 
I have no idea if its the same fault....but I had a very similar issue with my C209.....disconnecting the battery overnight cured it and it never came back.
I actually had the battery terminals off last night to ensure the car worked as it should this morning 😓. But thanks for the advice
 
Funny I actually had the fuse cover off for a few days while I was troubleshooting issues with the coolant level sensor! Should I bring it into the garage and maybe get a hairdryer into the SAM area?
A member last week managed to recover his (assumed) damp SAM in a Vito, by removing and drying, on a radiator I think.
While I didn't rate much for his chances of success it seems I was wrong.

Nowt to lose I guess.
 
Just a quick update all. I had cable tied a heat gun above the front Sam and put it on a gentle heat setting for 10 minutes and it had dried the residual water droplets off. I took out the small fuses (making sure to note which one went where) and when the fuses were put back in, it seems to have cured the problem!
 
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Until next time it is driven in the rain perhaps 😬
 
Unplug the alarm unit behind the front wheel arch.

Sounds daft , but when they go wrong they can have a very odd effect on the cars electrical system. Very quick and easy to do and it at least eliminates one possible cause.
 
Unplug the alarm unit behind the front wheel arch.

Sounds daft , but when they go wrong they can have a very odd effect on the cars electrical system. Very quick and easy to do and it at least eliminates one possible cause.
Is that the siren that's on the left hand side? I’ll actually give that a test too! Thanks!
 
and put a bag over the plug, and tape it.
 

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