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  #1  
Old 06-29-2015, 02:25 PM
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'75 240D - Parking brake light staying on when key off?

Hey guys..

Just picked up my first MB and trying to get some bugs worked out. The parking brake light stays on when the key is off. Goes off when the brake is released. Is this normal or shouldnt the light go off with the key?

Thanks
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  #2  
Old 06-30-2015, 08:37 AM
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Anybody know if this is normal?
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  #3  
Old 06-30-2015, 09:32 AM
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The light should only be activated when the ignition is on. You've got a relay sticking or someone has done a "hack" job on the wiring. The usual culprit is an aftermarket stereo/amp/alarm system.
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  #4  
Old 06-30-2015, 01:48 PM
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The under dash wiring is a mess... under hood is oem.

Anyone know where I can find a wiring diagram for this model?

Thanks
-Chris
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  #5  
Old 06-30-2015, 05:03 PM
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Location: Oregon
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Search google for "w115 service manual pdf" (without the quotation marks).
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'79 240D
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  #6  
Old 06-30-2015, 10:43 PM
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Got it. Now time to start digging through this rats nest. Another electrical question... is the alternator in these cars controlled directly by the regulator meaning they are always on?

Reason I asked is because I just found that my alt. isn't charging and wasn't sure if they had some form of ign. based trigger.
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Old 06-30-2015, 11:47 PM
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Standard diode controlled system. There is a replaceable voltage regulator mounted on the rear of the alternator. Should be three wires connected to the regulator. One is a constant 12V (large wire), one will be ignition controlled and the third is activated by the stator to indicate a charge status (idiot light).
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  #8  
Old 07-01-2015, 12:13 AM
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Hmm... perhaps the hackjob wiring under the dash is to blame for the lack of charging. The dummy light never lights when the key is in the "1" or "2" position... or when the car is running... from what I've read, that means there is an issue...

Alternator is doing nothing... battery voltage doesn't change at all when the engine is running.

I'll start tracing wiring tomorrow before having the alternator rebuilt.
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  #9  
Old 07-01-2015, 12:18 AM
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...apparently the bulb itself could be bad and cause the alternator not to charge?? Is that accurate?
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