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BigMikeT57 04-06-2004 11:29 PM

Battery Light when braking
Car is an '88 420SEL.
When trying to recreate an intermitant ABS light, I noticed the battery light would quickly "fade" on then off when hard braking.

Anyone have an idea what to check?

I checked the battery at idle and got 14.05 volts.

Ferdman 04-07-2004 08:32 AM

I would check the voltage regulator. How many miles since it was replaced?

BigMikeT57 04-07-2004 08:54 AM

Thanks Ferdman,

The car has 180k, of which only 8k are mine. No history avail.

I thought that a good voltage reading at idle indicated that the
voltage reg is OK. BTW, the battery is new.

moedip 04-07-2004 10:36 AM

Is your alternator belt tight?

G-Benz 04-07-2004 11:04 AM

I'm wondering if someone had tampered with the wiring behind the indicators at some point and miswired something.

It seems like the brake pad wear indicator would illuminate in that manner, unlike the battery indicator, which would just come on solidly, no matter what driving characteristic may occur.

autozen 04-07-2004 11:21 AM

G-Benz said it before I got a chance. I also think you are seeing the brake pad wear indicator light.


G-Benz 04-07-2004 12:08 PM

Still, the ABS system does require a considerable amount of electrical power to operate. If the charging system isn't up to the task, it may sense that there is a the system is low on current...although I would think the ABS light would come on too. :confused:

BigMikeT57 04-07-2004 04:15 PM

The belts were replaced right after I got the car, about 1 year/8k miles ago. I do have an intermittant ABS light, thats what I was trying to recreate when I saw the batt light come on.
When the ABS light comes on, it is solid and stays on 'till I shut down & restart.
The ABS problem is also the reason I had checked the batt voltage, and found 14.05 volts at idle.
This weekend I will clean the ABS sensors and check the belts.

BigMikeT57 04-07-2004 10:52 PM

I decided against driving the 420 today. When I got home from work we took it for a run, again trying to recreate the ABS and battery light problems.

On the way home the ABS came on followed by the SRS. Headlights dimmed considerably, then all the idiot lights came on.
Turned the corner to home and the car died.

Walked the half block to home and brought back my new batt. that I haven't put into the 300D yet. Fired it up and got it home.

OK I'm convinced. It's the voltage reg. right?

Question - Is the voltage reg the same as in a '83 300D 123?

I already have one for the 300D as a prevent. maint. item.

Thanks again for all of your help and expertise.

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