lately when i try to start my 1983 300D, the starter will turn and i can turn on the head lights but nothing else is getting electricity. no dash reading, no glowplug lights. no power to the windows, no a/c. no blinkers. nothing but the headlights will turn on. the engine started sometimes starts right up without any problem. once i start driving, i will hear a click and the buzzer will come on and all the power come back on. and my car sometimes will start fine sometimes it won't. now it's getting harder and harder to start? i not not sure where to look. any help is appreciated...

I'd start by reading up on how key switches fail.

Sixto
93 300SD

Remove battery cables and clean well and reinstall. Remove ground cable from body and clean well. Remove each fuse and clean contacts in fuse box then replace the fuses with correct rating with brass type fuses. The silver element type fuses oxidize where they contact the brass contacts in the fuse box, the brass ones are less likely to do this. If all this cleaning fails to correct this issue I would suspect the electrical portion of the ignition switch.

Sixto nailed this one. The electrical contacts in the "ignition" switch (Well, its a habit I still call them ignition switches!) gets worn and makes a flaky path to the instruments and buzzer and stuff. What will happen eventually, if you don't replace it, is the car will not even start, so you should probably learn where the three connection terminal is on the drivers side fenderwell, near the battery, and which pins to place a jumper wire on to manually activate the starter motor so you can drive the car when the key switch fails completely. I lived with a car that had a flaky key switch for a couple of years before I decided to replace the thing, along with a new lock cylinder. Its so nice to have a new lock and key in place of the 21 year old worn out ones

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

wow, you guys responded quick, thank you all for the advice. that was my first guess after reviewing the electrical diagram. just had to run it by everyone just to make sure. i am going to have to pull the dash and replace it today. thanks again.

you were spot on. the problem was the ignition switch. replace the switch and it started right up. now i need to work on vaccum problem. thank you guys for the help.