ALOHACOBRA

On a 87 560sl fuse #12 controls the antenna, radio and interior lights. None of these items was working. The fuse was blown. New fuse installed and immediately blew. Is this a short, if so where should I start looking?

alkraut

The symptoms you describe sound like a short. They can be very aggravating and time-consuming to find. The best approach is a methodical means to isolate which component is the culprit, as the short is most likely at the component, as opposed to the wiring (unless the wire was chafed or pinched).
First get a handfull of fuses. Start with the easiest to get to, being your interior lights. Remove the bulbs, and replace the fuse. If it does not blow, it has to do with the circuit to the lamp holder, or the lampholder itself. If the fuse still blows, try the next thing, being the antenna. You can access it thru the driver side panel in the trunk. Again remove the multi-wire connector and try the fuse again. If the problem is at the radio, it will be more work to remove it to unplug it. Assumming you find the problem component, you can remove and repair or replace it. Someone who knows the component might be able to fix it.

If you don't find the problem area, and just keep blowing the fuse, the short (to ground) is in the circuit, which includes wiring and connectors. Or it could be another component that uses that fused circuit. The cause of blown fuses is too much current draw. Thats "amps" of current. A short will draw high amperage from the battery and exceed the fuse, burning it out.
Finding the short to ground in the wiring is more work, and you may need help from an experienced technician.Good luck.

ALOHACOBRA

Thanks, its the trunk light. Took out the bulb and all is good. I just need to figure out if its the fixture or the wire.

Blackant

Hello all, first time on the site. I have an 88 560SL with 130000KM, delivered from MB to Australia. I notice the 2 courtesy lights in the front roof pillar do not have protected connections and can cause a short as well-this happened to me as the plastic had deteriorated a bit and the light becam loose. New light and insulated connector sorted out the problem

sargepepper

After looking through various answers to this fuse 12 problem, I finally found one where a solution was provided.

I was able to narrow down the short causing fuse 12 to blow to the dome lights (Not sure which one, I ran out of fuses). I did go ahead and order new fixtures, but it's great to find some support for that on the forum. Hopefully the new fixtures will resolve the problem. If not, I'll be posting my questions here.