Newbie here - Electrical Problem

[Blue190]

Hi All,

    I'm new to this Mercedes thing as this car is actually my wife's. I normally drive a 1965 dart conv so the tech level is just a wee bit different.
     So my problem is this... The car keeps running the battery dead, quickly. The first time it happened my wife was driving and the charging light came on. She freaked and came home but the battery was already too dead to restart. I charged it up again and the car started but only ran for about 5 minutes. Suspecting a bad alternator I took that to the auto parts store and had it tested. No dice. The alternator is fine. Since it's acting like somethings blocking the charging circuit is there a fusible link or circuit/relay that I should be inspecting and where is this?


(Edited by Blue190 at 5:06 am on Nov. 28, 2001)

 

[Neil Eglintine]

Newbie here

My first suspect would have been the alternator.

To run the battery flat that quickly from fully charged would require a huge electrical problem, probably smoke and flames. Therefore I suspect that the battery is duff.

Note that the diagnosis would be the same for the Dart. Is that an SP250 or a Dodge, by the way?

 

[Blue190]

Newbie here

Hi There Neil,

    It's a '65 red Dodge Dart Convertible. Ya I know it would take an interesting electrical problem to cause that. On the Dodge there is a fusilbe link that protects the cars components and will simply burn up if the voltage gets too high. The battery is good and taking a charge to 88% of it's capacity but really once the car starts it shouldn't need a battery at all as the alternator should be supplying all juice. I was wondering if the overvoltage relay in the fuse box does the same thing?

 

[Andy]

Newbie here

Hi

You really need to carry out a battery discharge test. You have already checked the alternater. In these cases do not assume anything. If the battery drops below 9.5v under load then there is a problem. If all is ok. Then you have to find the drain with the aid of a amp meter. And disconnect each fuse to find when the drain stops.

By the way you are incorrect about the car not needing the battery to stay running. Only diesels will run happily without the battery.

Regards
Andy @ www.mercedesservicing.com