I have an '83 300SD with 209K on it. I've had it for almost 8 years and the only repair I couldn't do myself was replacing the water pump. Last year I started having electrical problems and I just ignored them because they weren't a major inconvenience to me. Well last night as I was leaving work, I turned the headlights on and I noticed that the instrument light was not lit up. I tried jiggling the switch back and forth, but no luck.

A few months ago, the passenger side window will no longer go up or down. No big deal, the other 3 work.

Heater control and fan doesn't work. The only source of heat is the defrost now.

Interior lights and trunk light don't work, blowing fuses on this one.

So the story is that by not taking care of small problems, now I've got a lot of problems . I'm just wondering how much this will cost me?

This car is my 2nd car and I don't want this to turn into a bottomless pit that I throw money into. The engine and tranny and even the fuel injection pump are still going, so I just want the car to pass inspection at this point. At some point it's just not worth it to fix a car and I'm contemplating if I'm at that point now. Diesel here in my area is $2.89/ gallon and climbing. Your thoughts....please.

Try replacing all the fuses.

__________________
Adam Lumsden
(83) 300D
Vice-President of the MBCA International Stars Section

Some of your problems may be related (one failure causing several things to not work) but most are probably due to individual failures. As rg2098 suggests, check all of the fuses. Since you say that the interior and trunk lights don't work and are blowing fuses, you probably are already doing that. A search of this forum will bring up threads posted by others who have had and repaired all of your problems.

The passenger window is probably due to a bad switch, less likely a bad motor or a wiring problem. There was a DIY guide posted here somewhere recently about refurbishing the switches. It was not difficult to perform but the author recommended patience. The window motors themselves are fairly reliable but the associated wiring and such can get dirty, fray, etc., so electricity isn't getting to the motor. You can also remove the inner door panel and put 12 volts directly on the window motor to see if it works; if so, it's a case of electricity not getting to the motor.

The trunk/interior lights are on fuse #2 in my 1985 300D and probably in your car also. If that fuse keeps blowing then there is probably a short somewhere. You will have to trace everything on that fuse to see which one is shorted. A wire would have its insulation cut or frayed or a socket or switch could have come apart, allowing a hot lead to touch ground. It's a slow process but not difficult. The complete list of stuff that's on fuse #2:
antenna
clock
interior lights
hazard lights
radio
trunk lights
alarm
warning system
seat backrest locks (2-door coupe only?)

Heater control and blower problems are likely due to the ACC "amplifier" or electronic control module, which is part of the panel of switches for the climate control. This POS is discussed in many posts here. Resoldering the pc board in this thing often cures these problems. The fact that you have heat and (presumably) blower tells us that the other parts of the system are working, or at least trying to work.

The instrument lights could be due to fuse #1, to the light switch, or to the dimmer rheostat. If it isn't the fuse (which also powers your tail lamps and license plate lamps, by the way) then it is most likely the dimmer. Repair of this failure-prone rheostat is covered in this forum and does not seem to be a major problem although again some care and patience is required.

These problems are all ones that you can fix yourself and should cost very little except for your time.

Jeremy
.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Great info Jeremy, I need to make some time available to get this stuff figured out. Time seems to be a valuable commodity these days, for whatever the reason. Anyway at least I have somewhere to start. A wiring diagram would be a great place to start, hopefully there are some similarities with my '83 300SD and the ones covered in the Haynes Diesel 123 Manual.

At this point, I just want the car to pass inspection in 2 months. How long it will run is another question, as it had 172K on it when I bought it back in '99 for $4500. This car has been super reliable and has never left me stranded.

You are well aware of the Mercedes diesel reputation for building a long-lasting auto. However, and as it is said here over and over, you still must keep up with the maintenance. Fortunately, Mercedes has also designed our cars (the older ones) so that they can be maintained. Maybe the newer ones, too, but I have no experience.

As far as electrical diagrams go, the ones in my Haynes manual are OK if a little challenging to read. The factory diagrams are better and are available at http://mb.braingears.com.

[Braingears does work on Firefox (there have been posts that it works with IE only). Some of the urls in Braingears are written with backslashes instead of forward slashes; IE handles these but in Firefox you must manually rewrite the url.]

Finding the time to do the maintenance is another thing. If it were your airplane, you would never even raise the question, would you? Your Mercedes should get the same respect.

Jeremy

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970

Here you go:


http://mb.braingears.com/126_DISC1/program/ETM/126td83-85.pdf


You can download the entire .pdf file and store it on your machine if you have broadband.........don't try it with a dial-up.

I did some checking regarding the instrument lights not working and it turns out that the trip reset button somehow worked its way to the totally dimmed out position ! I didn't even know that the instrument lights were capable of being any dimmer than they already are, as they aren't bright enough for my liking.

When I get some time and ambition, I need to trace out the other problems, but the thought of tracing wires through the body panels is not the easiest thing.

Another positive note is that I decided to get the car inspected today, VA annual inspection, and it passed, so I'm good for another year. This 300SD is the longest I've ever held onto any vehicle, 7 years and counting. Long live the 300SD !

The probability that you've got a problem with a wire inside a body panel is usually remote. You can fix 99% of the electrical issues by dealing with the switch or the device........or their connectors.

Did you download the .pdf file?

That PDF is simply awesome and without it I wouldn't know where to start for sure. Thanks for the link.

Just post on this thread if you have problems with the electrical devices on that vehicle.

I'm pretty familiar with it.