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Old 27th September 2019, 13:29   #21
HarryM1BYT
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Originally Posted by Odd Job View Post
I'll try and see if the switch is sticky first port of call.

What is the LSM please Artic?
Its not a physical switch, its an Hall Effect sensor - it senses the metal of the pedal being close to it.

LSM is the Light Switch Module, the module which controls the cars lighting system, a little computer. The brake 'switch' signals the LSM, the LSM then puts the brake lights on.



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Old 27th September 2019, 14:28   #22
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I suspect a bad connection on fuse 13 then, when you removed it to check you have probably made a decent connection and all is now well.


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Old 27th September 2019, 20:35   #23
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I suspect a bad connection on fuse 13 then, when you removed it to check you have probably made a decent connection and all is now well.


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Yes sounds like the old late fusebox problem of corrosion that builds up on the fuses

Removing the fuse to check and replacing it has probably re-established the connection.

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Old 28th September 2019, 01:38   #24
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OK. Plenty to take in there then.
A hall switch? That'll explain why when I looked at pics of one it didn't resemble any brake light switch I'd seen before!
As to the fuses and corrosion, yet another "common" problem?

Many thanks everyone. I'll continue my daily checks for the moment, and I'll see about a new brake light switch if it occurs again.

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Old 30th September 2019, 07:40   #25
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Well,

It's happened again!
After checking every morning before setting off, all was good. This morning, nice and damp, and cold, and the brake lights are on!

So, I set off to work, put my wipers on, and on the auto setting the wipers were going nuts as if on fast speed. It was damp but not raining.
So, I'm thinking that the problem is on the same circuit as the wipers??

Anyway, about a quarter of a mile down the road, the wipers stopped being stupid, so I pulled up at the side of the road, and guess what? The brake lights are off!

OK, anyone got any idea what module or gizmo is getting damp in and playing stupid please??

Many thanks

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Old 30th September 2019, 09:45   #26
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... anyone got any idea what module or gizmo is getting damp in and playing stupid please?
It's a long shot but the wipers are controlled by the BCU and the brake lights by the LSM and both are on the K-bus.

You say that the wipers were in 'auto' mode. Do you mean delayed wipe or rain sensing operation? If the latter, it may be a red herring. That happens on my Citroën and I've seen it on a nearly new BMW 3 series as well.

You have identified that the fault occurs when there is high humidity. Have you checked the connectors of the BCU and LSM for security and condition?

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Old 30th September 2019, 10:41   #27
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The wipers were in rain sensing mode.

I've not had chance to check anything today.

The weekend just gone was like monsoon season, and I didnt use the car on Sunday at all.
I found I'd got the same issue this morning as I was about to go to work.
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Old 30th September 2019, 11:29   #28
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There's a few possibilities here.
The rain sensing wiper ECU behind the rain sensor is prone to faults but doesn't usually cause those type of problems. If you unplug it it will revert to normal intermittent operation which could be helpful to try to isolate the fault.

Have you checked the earth connections behind the A pillar lower covers and check for corrosion. This can cause similar kinds of problems, similar to below

Has anything been added to the car, even if it's been ok for a while, recently had a car that had lots of added wiring for various upgrades. It had intermittent problems with locking and wipers, turned out to be a poor added earth that was making intermittent contact. The added wiring had been in place for quite some time before the problems began

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Old 30th September 2019, 12:07   #29
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Thanks Russ,

Nothing has been added to the car electric wise apart from a replacement gold resister fitted by Artic at the last Nano meet.

I've only had the car just over a month, goodness knows how long it's had the problem.
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Old 14th October 2019, 07:46   #30
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Monday Morning blues!

Same story, seems to be on a Monday morning after a very wet weekend, very damp.
A little different this morning.
I started the car up, no brake lights! Great!
I started going around the car with a squeegee to remover the condensation off the windows, got to the rear of the car, and the brake lights are doing a disco!

They stopped messing about within 5 mins and I was on my way.

Really weird!
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