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Discussion Starter · #1 ·
Hi, I have a problem with my brake lights on my E36. Its an ealy 1995 model, with on board computer. The computer does not show any problems (mind you I have never seen it show any problems in the 2 years I have owned it!) and there are no warning lights on the dashboard. Someone told me the other day I had a brakelight out so I went to investigate to find neither of these work.

I have tested the bulbs by putting them into the reversing lights and they work fine. I have checked all the contacts and they also seem fine. I used an ammeter to check if there was voltage at the contacts when the brake is pressed and sure enough there is 12 volts there when the pedal is pressed however when I put a bulb in, it wont light it. Just make sure it wasn;t the bulb carrier, i connected 2 pieces of wire from the contacts to a bulb and it still didn't work!!!! Please help, I have run out of ideas, I cant understand why if there is 12volts at the contacts it wont light the bulb!!!! Any help much appreciated, I have read through previous posts whioch talk alot about the switch failure, but surely it isnt that is it if it still pushes the voltage to the contacts as it should???!!!!!!

Please help!!! Im as a loss with it.

Cheers
 

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Out of interest, what reading do you get when the pedal is not pressed?

I'm not entirely sure what happens with regards to the switch but perhaps the bulbs rely on a signal from this before they illuminate:confused

Sorry, i'm just guessing to try and assist with ideas as to what the failure may be?
 

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Discussion Starter · #3 ·
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The reading when the pedal is not pressed is 0 volts which was what you would expect I guess! Really frustrating though!!!!! Does anybody think it could be the switch???
 

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Because you're getting zero volts when not pressed and 12 when it is that to me would indicate the switch is working.

How very strange???
 

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Sounds like you have no earth, if like you say you have power to the bulb but no bulb work then it must be a earth fault. connect a test light to the + side of the battery and get testing
 

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Or the switch is braking down under load. The switch may be high resistance and a test meter is VERY high resistance so it will not drag the voltage down like a bulb will. More likely no earth tho.

If you have no luck get a bulb, solder 2 wires to it and use that as your test meter, check live to chassis and see if it illuminates. Then check live to the bayonet earth in the lamp holder. Go from there :)

HTH.
 

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Discussion Starter · #9 ·
Thanks

Thanks for your help guys, if I get any joy I will let you know. If anybody else comes up with any ideas please let me know!!! Otherwise, its a trip to the local auto-electricians soon!!
 

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To be honest no.

I have no wiring diagram for the car in question but normaly i5s hard wired, safety features should not be connected via any computor or logic controler to keep things simple and less prone to failure.

However, BMW do some fancy stuff now, as do most manufcactorers in the last few yesrs. Electric connections are all done via a network (CAN Open) and nothing is hard wired now. By changing the software code in the can bus master controler you can make any thing do anything. If you want the lights to flash 4 times if your hand brake is off and you lock the door, no problem just ad a line of code, etc. So it wouldnt shock me to find BMW have told the brake lights only to light for a few seconds after the car becomes stationary so you dont get dazzled behind it in traffic or something.

Also be aware, many cars now switch the earth not the live (Synch switching) so you need to make sure the earth you use with your test meter is the one in the bulb holder not the cars chassis in general.

If you are in the midlands pop it to me I will sort you out :)
 

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Discussion Starter · #14 ·
Sorted!!!! It was the brake light switch in the end!! Still dont get how it can have been sending 12v yet not lighting the buld but hey!!! Took the connector off the pedal and bridged the two brake light wires, the other two are for the on-board cmputer and hey presto!!! Quite surprised, GSF stocked them and only 11 quid so, jobs a goodun. Thanks for all your help.
 

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Sorted!!!! It was the brake light switch in the end!! Still dont get how it can have been sending 12v yet not lighting the buld but hey!!! Took the connector off the pedal and bridged the two brake light wires, the other two are for the on-board cmputer and hey presto!!! Quite surprised, GSF stocked them and only 11 quid so, jobs a goodun. Thanks for all your help.
Excellent, A very big WELL DONE to you:thumbsup
 
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