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Discussion Starter #1
Howdie All...two issues? Or one?

ABS indicator light is on while driving.

In addition, the battery is not charging so I am considering replacing alternator.

In owners manual I read that when charging voltage falls below 10volts, ABS indicator light will be illuminated.

So to get to my question...while I am thinking all along that ABS is defective, do you think there’s a chance the ABS indicator light might go out if I do something as simple as replace alternator?

Your input greatly appreciated.
Thx
Chris
 

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1973 450 SL
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2,062 Posts
Yes. Owner's manual would lead me to believe the same thing. Start/Run bus power to the ABS or "ANTILOCK" bulb is protected by fuse 7 via red/black lead. Switched ground for that bulb is provided at pin 29 of ABS Electronic Control Unit via brown/yellow lead. Brown is always a ground; brown with a (any color) hash is a switched ground.

ETM does not provide detail inside the ABS Electronic Control Unit but your owner's manual indicates it will switch pin 29 to ground with less than 10V available at pin 15 (voltage monitor input). Pin 15 has a blue/red lead to a junction tied to the alternator D+ (61) circuit.
 

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Discussion Starter #4
Thanks cushjbc....I will have to look at that. I replaced the alternator and the ABS light is still on. It might be the module after all or something definitely ABS related.
Thanks Jyuma...I did remove the regulator and saw that the brushes were well worn but after assuming alternator was original, I just replaced the whole thing.
Thanks again for all the advice.
 

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1986 560SL with M120 V12 Engine, 1988 560SL Stock
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10,432 Posts
Howdie All...two issues? Or one?

ABS indicator light is on while driving.

In addition, the battery is not charging so I am considering replacing alternator.

In owners manual I read that when charging voltage falls below 10volts, ABS indicator light will be illuminated.

So to get to my question...while I am thinking all along that ABS is defective, do you think there’s a chance the ABS indicator light might go out if I do something as simple as replace alternator?

Your input greatly appreciated.
Thx
Chris
Start by measuring the voltage output. should be about 14v.
 

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Premium Member
1986 560SL with M120 V12 Engine, 1988 560SL Stock
Joined
·
10,432 Posts
Thanks cushjbc....I will have to look at that. I replaced the alternator and the ABS light is still on. It might be the module after all or something definitely ABS related.
Thanks Jyuma...I did remove the regulator and saw that the brushes were well worn but after assuming alternator was original, I just replaced the whole thing.
Thanks again for all the advice.
Check OVP relay
 

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Premium Member
1983 380 SL
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3,032 Posts
Thanks cushjbc....I will have to look at that. I replaced the alternator and the ABS light is still on. It might be the module after all or something definitely ABS related.
Thanks Jyuma...I did remove the regulator and saw that the brushes were well worn but after assuming alternator was original, I just replaced the whole thing.
Thanks again for all the advice.
Almost can't go wrong replacing a 30 something year old alternator but be weary of being pulled onto those rocks... everything in the car is 30 something years old.
 
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