Everything electric goes on and off
 

I drive a 1983 300SD with 300k miles. Driving down the highway yesterday, my radio quit playing. I then noticed that the speedometer and all gauges did not work, the blinkers, windshield wipers, headlights, taillights, etc did not work---nothing electrical worked. Several miles later, everything began to work again. When I got home, I pulled the battery out, tested it, found it to have no charge---completely dead, so I replaced it with a new battery. I had installed a rebuilt alternator two months ago. After installing the new battery, the same thing occured with the electrical system going off within one mile of driving after I had installed the new battery. Where should I start to troubleshoot the problem? What are the most likely things that this could be?

Thanks, Boxcar

boxcar,

If the battery is dying quickly, you might have a short in the system somewhere that is eating the battery when it is just sitting there. Do you have a multimeter or some way to check voltage on the battery, and check to see if there is a drain on the battery when the car is shut off? Some things, like the clock and any alarm system will draw a little current, but you are seeing some significant current draw to kill a new battery in a day.

Did the old battery work ok for a few months and then die, followed by a new battery dying in a matter of hours? Was the new battery fully charged before it died?

Have you checked the connections to the alternator? There is a plug that is held in by a spring clip and a small wire that connects to a screw on the body of the alternator. If these have worked loose, it is not likely that the battery would be ok after a few starting episodes, as the alternator may not charge at all depending on which wires might not be connected properly.

Also, a bad ground would interfere with charging and possibly contribute to the symptoms you have experienced. The ground for the battery is on the inner fender on the passenger side, easily traced from the negative pole of the battery. Unscrew the bolt to the fender and clean any corrosion on the bolt, the fender and connector, then put it back together.

Hope this helps; if you have any more information please post it so others can add to the list of potential solutions. Good luck, Jim

Might be bad voltage regulator brushes. Do you have an oil leak that allows oil into the alternator? Could be affecting the contact of the regulator brushes.

Sixto
91 300SE
87 300SDL
81 300SD

sounds like a bad ground