82 300d gradual electrical failure

My gifted 82 300d seems to have cancer of the electrical systems. First windows, then blowers and heat/cool, now locks. Where do I start looking (Seems to originate in the panel between the seats)? Is this too much for a mech head girl with no time and no garage in a cold place? Car came from my brothers estate, know he replaced a lot of engine parts, hate to dump it, but need to be realistic.

Forums

Body and Interior Specific Aid

Chassis Model Number

W123

Start with new fuses

Start by cleaning the fuse box connections AND replacing all the fuses. CLICK HERE to view our fuse replacement kit with instructions. The door locks are not electrical. They are run by vacuum and often develop leaks. My guide for the door locks with walk you through finding and repairing those leaks. CLICK HERE to view this manual. Good luck, Kent Bergsma

Fuses first, kit well worth it!

As Kent said, start with his fuse kit and an additional tip I've learned is the little fiberglass sanding pen from radio shack to clean the terminals for the fuses before installing new ones.

The switches fail easily for the windows...the pivot point cracks (old switches) or they get mushy (newer switches.) Believe it or not, for both switches, the dealer is a great place if you go to the parts dept. as a mech head.

There is a point to this: Beware the after market radio as well if you have one! Every one I've seen has "hacked" up wires through the fader or other locations for power. Pre '86, the factory setup was four speakers but TWO channel output from the factory radio. Any aftermarket radios after about 86/87 used a bridged four channel setup....hooking these up through the factory fader is BAD if it is not rewired as the early cars used a common ground for all speakers and not a bridged setup w/separate ground. In 83 or so, there is a stern warning on the factory radio that it uses a bridged TWO channel output and an admonition NOT to hook the grounds together (the English is laughable, but the German makes sense.) As power is conveniently available at the power window switches of the center console, perhaps a crimp joint or something else has given out. There is little room under there for the switch harnesses.

Another thing to really check out is the headlight switch. It is the electrical center of these cars. Two or three 10ga 30amp wires coming from the battery or fuse box. These terminals heat up and it will be obvious as the plastic casing on the back will be puckered up. Terminals 30a/30b can give you some insight as to which area is causing the issue if you have an electrical diagram handy. The CD is only $20 from mbusa but is worthless for pictures and, many times, for diagrams. It is useful, nonetheless and cheap.